NativeAOT readiness

[AArnott]

We should vet this library for NativeAOT readiness.

See https://github.com/dotnet/Nerdbank.Streams/pull/783/files for an example of how this can be done.

[eerhardt]

One place that will need to be addressed is:

vs-threading/src/Microsoft.VisualStudio.Threading/InternalUtilities.cs

Lines 254 to 287 in d99d64b

	/// <summary>
	/// A helper method to get field's value given the object and the field name.
	/// </summary>
	private static object? GetFieldValue(object obj, string fieldName)
	{
	Requires.NotNull(obj, nameof(obj));
	Requires.NotNullOrEmpty(fieldName, nameof(fieldName));
	FieldInfo? field = obj.GetType().GetTypeInfo().GetDeclaredField(fieldName);
	if (field is object)
	{
	return field.GetValue(obj);
	}
	return null;
	}
	/// <summary>
	/// The field names of "async state machine" are not fixed; the workaround is to find the field based on the suffix.
	/// </summary>
	private static object? GetStateMachineFieldValueOnSuffix(IAsyncStateMachine stateMachine, string suffix)
	{
	Requires.NotNull(stateMachine, nameof(stateMachine));
	Requires.NotNullOrEmpty(suffix, nameof(suffix));
	IEnumerable<FieldInfo>? fields = stateMachine.GetType().GetTypeInfo().DeclaredFields;
	FieldInfo? field = fields.FirstOrDefault((f) => f.Name.EndsWith(suffix, StringComparison.Ordinal));
	if (field is object)
	{
	return field.GetValue(stateMachine);
	}
	return null;
	}

This is using reflection to inspect a bunch of async state machine fields. If this code is only used for diagnostics, maybe the warnings can be suppressed? Or hidden behind a feature switch.