fix: Optimizes OPL using string interpolation (#1041)

## Breaking Changes (New API)
ObjectPropertyList supports the following API:
```cs
list.Add(500000);
list.Add(500001, stringArgument);
list.Add("Some text");
list.Add($"Some text with {argument}");
list.Add(500002, $"{arg1}\t{arg2}");
```

## Notes
1. All API uses that require a formatter like this:
    ```cs
    list.Add(500002, "{0}\t{1}", arg1, arg2);
    ```
    Should be changed to use string interpolation, for example:
    ```cs
    list.Add(500002, $"{arg1}\t{arg2}");
    ```
2. The following paradigm should no longer be used:
    ```cs
    list.Add(1061170, prop.ToString()); // strength requirement ~1_val~
    ```
    The new string interpolation API will avoid having to convert the argument to a string before writing it to the packet. Instead use the following:
    ```cs
    list.Add(1061170, $"{prop}"); // strength requirement ~1_val~
    ```

### Benchmarks
```cs
|                         Method |     Mean |   Error |  StdDev |  Gen 0 | Allocated |
|------------------------------- |---------:|--------:|--------:|-------:|----------:|
|                BenchmarkOldOPL | 241.0 ns | 0.56 ns | 0.47 ns | 0.0105 |      88 B |
| BenchmarkStringInterpolatedOPL | 199.9 ns | 2.44 ns | 2.39 ns |      - |         - |
```

### Changes
- [X] Removes crash in STArray.Return when array is null.
- [X] Fixes NPE in OPL when entity is null. Serial in packet will be 0 when entity is null.
- [X] Fixes NPE in AosAttributes when Parent is null.
- [X] Changes OPL to use string interpolation.
- [X] Introduces `IPropertyList` to allow extending PropertyList for other uses.

Projects/UOContent/Items/Skill Items/Musical Instruments/BaseInstrument.cs

@@ -359,7 +359,7 @@ namespace Server.Items
             m_Instruments[from] = item;
         }
 
-        public override void GetProperties(ObjectPropertyList list)
+        public override void GetProperties(IPropertyList list)
         {
             var oldUses = m_UsesRemaining;
             CheckReplenishUses(false);
@@ -376,7 +376,7 @@ namespace Server.Items
                 list.Add(1060636); // exceptional
             }
 
-            list.Add(1060584, m_UsesRemaining.ToString()); // uses remaining: ~1_val~
+            list.Add(1060584, $"{m_UsesRemaining}"); // uses remaining: ~1_val~
 
             if (m_ReplenishesCharges)
             {