feat: Adds grid support for the DynamicGump system (#2306)

### Summary 

- Adds a new grid layout system for DynamicGump with zero heap allocations
 - Migrates SpawnerControllerGump from legacy GumpGrid to DynamicGump
 - Migrates CommandListGump from BaseGridGump to DynamicGump
 - Removes legacy GumpGrid (no longer needed)

 ### New Grid Layout Components

 | Component | Purpose |
 |-----------|---------|
 | `GridCell` | Value type for cell bounds (x, y, width, height) |
 | `GridSizeSpec` | Parses CSS-like sizing specs ("10*", "*", "100") |
 | `GridCalculator` | Computes track positions using stackalloc |
 | `ListViewLayout` | Pagination + column layout for list views |
 | `GridBuilderExtensions` | Extension methods accepting `GridCell` |
 | `GridEntryStyle` | Styling properties for BaseGridGump migration |
 | `GridEntryExtensions` | Entry methods matching BaseGridGump patterns |

 ### Memory Impact

 | Component | Legacy | New |
 |-----------|--------|-----|
 | Grid storage | ~200 bytes heap | 0 bytes (stackalloc) |
 | Column/Row lists | ~400 bytes heap | ~128 bytes stack |
 | ListView | ~300 bytes heap | ~64 bytes stack |
 | **Total per render** | **~900 bytes heap** | **0 bytes heap** |

 ### Test plan

 - [x] All 21 gump tests pass
 - [x] Build succeeds with no warnings
 - [ ] In-game verification of SpawnerControllerGump
 - [ ] In-game verification of CommandListGump (HelpInfo command)

Projects/Server/Utilities/Utility.cs

@@ -209,7 +209,7 @@ public static partial class Utility
         var span = chars.AsSpan(0, str.Length);
         str.CopyTo(span);
 
-        FixHtml(span);
+        span.FixHtml();
 
         var fixedStr = span.ToString();
         STArrayPool<char>.Shared.Return(chars);
@@ -243,7 +243,7 @@ public static partial class Utility
 
         if (!str.IsNullOrWhiteSpace())
         {
-            FixHtml(span);
+            span.FixHtml();
         }
 
         return formattable;