Resolve UnmanagedArray<T> obsolescence warnings

[VaclavElias]

While generating documentation using docfx, I encountered 14 warnings related to the use of UnmanagedArray<T>, which has been marked as obsolete. The recommended approach is to obtain Memory<T> using GC.Allocate*Array or through a Stride-specific allocator mechanism. Addressing these warnings will enhance our codebase's cleanliness and maintainability. Below are examples of the warnings:

1. warning: D:\Projects\GitHub\stride\sources\engine\Stride.Audio\CompressedSoundSource.cs(20,24): warning CS0618: 'UnmanagedArray<short>' is obsolete: 'Obtain Memory<T> using GC.Allocate*Array or a Stride-specific allocator mechanism.'
2. warning: D:\Projects\GitHub\stride\sources\engine\Stride.Physics\IHeightStickArraySource.cs(26,24): warning CS0618: 'UnmanagedArray<T>' is obsolete: 'Obtain Memory<T> using GC.Allocate*Array or a Stride-specific allocator mechanism.'
3. warning: D:\Projects\GitHub\stride\sources\engine\Stride.Physics\HeightStickArraySourceFromHeightmap.cs(34,31): warning CS0618: 'UnmanagedArray<T>' is obsolete: 'Obtain Memory<T> using GC.Allocate*Array or a Stride-specific allocator mechanism.'
4. warning: D:\Projects\GitHub\stride\sources\engine\Stride.Physics\ByteHeightStickArraySource.cs(45,31): warning CS0618: 'UnmanagedArray<T>' is obsolete: 'Obtain Memory<T> using GC.Allocate*Array or a Stride-specific allocator mechanism.'
5. warning: D:\Projects\GitHub\stride\sources\engine\Stride.Physics\Shapes\HeightfieldColliderShape.cs(129,16): warning CS0618: 'UnmanagedArray<short>' is obsolete: 'Obtain Memory<T> using GC.Allocate*Array or a Stride-specific allocator mechanism.'
6. warning: D:\Projects\GitHub\stride\sources\engine\Stride.Physics\Shapes\HeightfieldColliderShape.cs(131,16): warning CS0618: 'UnmanagedArray<byte>' is obsolete: 'Obtain Memory<T> using GC.Allocate*Array or a Stride-specific allocator mechanism.'
7. warning: D:\Projects\GitHub\stride\sources\engine\Stride.Physics\Shapes\HeightfieldColliderShape.cs(133,16): warning CS0618: 'UnmanagedArray<float>' is obsolete: 'Obtain Memory<T> using GC.Allocate*Array or a Stride-specific allocator mechanism.'
8. warning: D:\Projects\GitHub\stride\sources\engine\Stride.Physics\ShortHeightStickArraySource.cs(45,31): warning CS0618: 'UnmanagedArray<T>' is obsolete: 'Obtain Memory<T> using GC.Allocate*Array or a Stride-specific allocator mechanism.'
9. warning: D:\Projects\GitHub\stride\sources\engine\Stride.Physics\Shapes\HeightfieldColliderShape.cs(42,86): warning CS0618: 'UnmanagedArray<short>' is obsolete: 'Obtain Memory<T> using GC.Allocate*Array or a Stride-specific allocator mechanism.'
10. warning: D:\Projects\GitHub\stride\sources\engine\Stride.Physics\Shapes\HeightfieldColliderShape.cs(47,86): warning CS0618: 'UnmanagedArray<byte>' is obsolete: 'Obtain Memory<T> using GC.Allocate*Array or a Stride-specific allocator mechanism.'
11. warning: D:\Projects\GitHub\stride\sources\engine\Stride.Physics\Shapes\HeightfieldColliderShape.cs(52,86): warning CS0618: 'UnmanagedArray<float>' is obsolete: 'Obtain Memory<T> using GC.Allocate*Array or a Stride-specific allocator mechanism.'
12. warning: D:\Projects\GitHub\stride\sources\engine\Stride.Physics\FloatHeightStickArraySource.cs(35,31): warning CS0618: 'UnmanagedArray<T>' is obsolete: 'Obtain Memory<T> using GC.Allocate*Array or a Stride-specific allocator mechanism.'
13. warning: D:\Projects\GitHub\stride\sources\engine\Stride.Physics\Data\HeightfieldColliderShapeDesc.cs(81,24): warning CS0618: 'UnmanagedArray<T>' is obsolete: 'Obtain Memory<T> using GC.Allocate*Array or a Stride-specific allocator mechanism.'
14. warning: D:\Projects\GitHub\stride\sources\engine\Stride.Physics\UnmanagedArrayExtensions.cs(18,41): warning CS0618: 'UnmanagedArray<T>' is obsolete: 'Obtain Memory<T> using GC.Allocate*Array or a Stride-specific allocator mechanism.'