[sre] Add MonoDynamicImageTokCollision arg to mono_dynamic_image_register_token

[sre] Add MonoDynamicImageTokCollision arg to mono_dynamic_image_register_token

The new argument controls what should happen when the given token is already
present.

In some situations it's expected that we either see the same object, or we
unconditionally want to replace it (for example if we previously registered a
TypeBuilder or a MethodBuilder, after the type or method is created, we will
re-register the RuntimeType or MonoMethod in its place).  In other cases (for
example when a module references a MonoMethod from a different assembly), we
may still call `mono_image_create_token()` multiple times but we expect to see
the same MonoMethod object.