Support unsafe accessors for static methods when they become available.

[eiriktsarpalis]

Support for unsafe accessors of static methods was added in .NET 10 via the new UnsafeAccessorTypeAttribute. The source generator should be updated to leverage that once .NET 10 gets released.

We should update the logic here:

PolyType/src/PolyType.SourceGenerator/Parser/Parser.ModelMapper.cs

Lines 562 to 568 in 648dd23

	CanUseUnsafeAccessors = _knownSymbols.TargetFramework switch
	{
	// .NET 8 or later supports unsafe accessors for methods of non-generic types.
	// .NET 10 or later supports unsafe accessors for static methods cf. https://github.com/eiriktsarpalis/PolyType/issues/220
	var target when target >= TargetFramework.Net80 => !m.Method.ContainingType.IsGenericType && !m.Method.IsStatic,
	_ => false
	},

such that net10.0 targets also support static methods for unsafe accessors. Then the codegen should take advantage of the new UnsafeAccessorTypeAttribute.

[eiriktsarpalis]

Parking this, since support for generic types in UnsafeAccessorTypeAttribute is currently sketchy.