Annotate several DirectX methods as SuppressGCTransition

[tannergooding]

This annotates several DirectX methods with SuppressGCTransition where they meet all the requirements:

• Native function always executes for a trivial amount of time (less than 1 microsecond).
• Native function does not perform a blocking syscall (for example, any type of I/O).
• Native function does not call back into the runtime (for example, Reverse P/Invoke).
• Native function does not throw exceptions.
• Native function does not manipulate locks or other concurrency primitives.

Notably, that effectively restricts it to Get* methods that are just return field.