refactor: Changes BaseCreature to the SerializationGenerator (delta save requirement) (#2611)

The pure SerializationGenerator conversion of `BaseCreature`, split out of #2592 so it can serve as the reference for converting every other large hand-written class in the Delta Saves project (#7, phase 3). Two behaviour changes from #2592 are deliberately not here and follow in their own PRs on top of this one: `SpeedClass`, and the collapse of `ControlMaster`/`SummonMaster` into one reference (a creature can lose or keep either independently: Blade Spirits and Energy Vortexes are summoned but never controlled, EnragedCreature and talisman summons keep a summon master with neither flag set).

## What this is

- `BaseCreature` becomes `[SerializationGenerator(23, false)]` with a `[SerializableField]` per serialized slot and `[SaveFlag]` elision on nearly every field, so a stock creature serializes to its version plus flags. Field orders run 0..53 with no gaps (54 fields).
- The hand-written reader stays as `private void Deserialize(IGenericReader reader, int version)` for every pre-codegen version (0..22); post-codegen bumps use `MigrateFrom` from here on. `[AfterDeserialization]` carries the post-load fixups main did after reading (stat timers, AI type, followers, reacquire seeding).
- `ControlMaster` and `SummonMaster` stay two independent fields with main's semantics, each elided when null.
- `DamageMin`/`DamageMax`/`ActiveSpeed`/`PassiveSpeed` are no longer virtual (nothing in the tree overrode them); comments swept to the constraints that matter.
- Direct writes to serialized backing fields outside the generated setters (`SetDamage`, `SetResistance`, the move-speed helpers, the loot flag, feed loyalty, the delete timer) call `this.MarkDirty()`, matching the #2609 standard, so the class is ready for delta saves once `Mobile` is audited.
- Schema `Server.Mobiles.BaseCreature.v23.json` regenerated by the tool (a second run produces no diff).

## Deferred to follow-up PRs

SpeedClass: the serialized `_speedClass` field, `DefaultSpeedClass` replacing the type constant, `ApplySpeedClass`/`OnSpeedClassChange`, "None means custom", the four-speeds-as-one-block elision, `NPCSpeeds.FindEntry(SpeedLevel)`, the constructor fallback to Medium, and their tests.

Master references: serializing one `Master` with a `Controlled`/`Summoned` fan-out and the `SetControlMaster` lockstep.

## Tests

UOContent.Tests 776 / Server.Tests 855 green. `BaseCreatureSerializationTests` covers: a default creature elides to version + flags; a populated creature round-trips with exact byte consumption; back-to-back saves are byte-identical; an uncontrolled summon keeps its SummonMaster; byte-authentic v22 legacy streams (replicas of main's `Serialize`) load through the legacy reader for a wild tamable, a controlled pet, a controlled summon with an anchored `SummonEnd`, and a summon-master-only creature (the EnragedCreature shape); a running delete timer round-trips through `[DeserializeTimer]`; `Friends`, `CurrentWayPoint` and `HomeMap` round-trip; a `BaseVendor` stub round-trips the generated BaseVendor v2 → generated BaseCreature v23 chain.

## Behaviour notes for reviewers

- `ActiveMoveSpeed`/`PassiveMoveSpeed` getters return the raw override (0 = inherit); `CurrentMoveSpeed` is the resolved pace.
- Speeds elided as table defaults re-snap to the current `npc-speeds.json` on load, so table edits reach unmodified spawns on restart.
- `GetSpeeds` no longer throws on the save/load path when the table has no entry for the type: saves elide against the creature's own values and loads keep the stream. Construction still throws (`InvalidOperationException`, was `KeyNotFoundException`). An elided load with no table entry would otherwise resume at speed 0, so `[AfterDeserialization]` logs once and paces it at Medium.
- `virtual` removed from `ActiveSpeed`, `PassiveSpeed`, `DamageMin`, `DamageMax` (no overrides in the tree; forks may have some).
- `ControlMaster`, `SummonMaster`, `ControlOrder`, `Tamable`, `IsParagon` are `[SerializableProperty]` over hand-written setters because follower bookkeeping must run before the assignment, which a `fieldChanged` hook cannot express; the wire format is identical.

## Prerequisites for cherry-picking
#2609 (BaseVendor is already generated on top of BaseCreature) and SerializationGenerator 4.1.0.

Projects/UOContent.Tests/Tests/Mobiles/AI/MoveSpeedTests.cs

@@ -57,8 +57,9 @@ public class MoveSpeedTests : IDisposable
     {
         var bc = NewCreature();
 
-        Assert.Equal(0.3, bc.ActiveMoveSpeed);
-        Assert.Equal(0.6, bc.PassiveMoveSpeed);
+        // 0 = no override; the resolved pace comes from CurrentMoveSpeed.
+        Assert.Equal(0, bc.ActiveMoveSpeed);
+        Assert.Equal(0, bc.PassiveMoveSpeed);
         Assert.Equal(bc.CurrentSpeed, bc.CurrentMoveSpeed);
     }
 
@@ -96,8 +97,8 @@ public class MoveSpeedTests : IDisposable
 
         bc.SetSpeed(0.2, 0.4);
 
-        Assert.Equal(0.2, bc.ActiveMoveSpeed);
-        Assert.Equal(0.4, bc.PassiveMoveSpeed);
+        Assert.Equal(0, bc.ActiveMoveSpeed);
+        Assert.Equal(0, bc.PassiveMoveSpeed);
     }
 
     [Fact]
@@ -108,8 +109,10 @@ public class MoveSpeedTests : IDisposable
 
         bc.ActiveMoveSpeed = 0;
 
-        Assert.Equal(0.3, bc.ActiveMoveSpeed);  // inheriting again
+        Assert.Equal(0, bc.ActiveMoveSpeed);    // inheriting again
         Assert.Equal(0.9, bc.PassiveMoveSpeed); // other override untouched
+        bc.SetCurrentSpeedToActive();
+        Assert.Equal(0.3, bc.CurrentMoveSpeed); // resolves to the think clock
     }
 
     [Fact]
@@ -121,7 +124,7 @@ public class MoveSpeedTests : IDisposable
         bc.ScaleMoveSpeed(1.0 / 1.2);
 
         Assert.Equal(0.5, bc.ActiveMoveSpeed);
-        Assert.Equal(bc.PassiveSpeed, bc.PassiveMoveSpeed); // still inheriting, not 0 * scalar
+        Assert.Equal(0, bc.PassiveMoveSpeed); // still inheriting, not 0 * scalar
     }
 
     [Fact]
@@ -185,8 +188,8 @@ public class MoveSpeedTests : IDisposable
 
         bc.MigrateMoveSpeeds();
 
-        Assert.Equal(0.35, bc.ActiveMoveSpeed);
-        Assert.Equal(0.6, bc.PassiveMoveSpeed);
+        Assert.Equal(0, bc.ActiveMoveSpeed); // still inheriting the (tuned) think clock
+        Assert.Equal(0, bc.PassiveMoveSpeed);
     }
 
     [Theory]
@@ -211,9 +214,9 @@ public class MoveSpeedTests : IDisposable
         var reader = new BufferReader(buffer);
         copy.Deserialize(reader);
 
-        // The v22 tail is the last block; exact consumption catches any offset mistake.
+        // The BaseCreature tail is the last block; exact consumption catches any offset mistake.
         Assert.Equal(buffer.Length, reader.Position);
-        Assert.Equal(overridden ? 0.45 : 0.3, copy.ActiveMoveSpeed);
-        Assert.Equal(overridden ? 0.9 : 0.6, copy.PassiveMoveSpeed);
+        Assert.Equal(overridden ? 0.45 : 0, copy.ActiveMoveSpeed);
+        Assert.Equal(overridden ? 0.9 : 0, copy.PassiveMoveSpeed);
     }
 }