Add extension methods to run guaranteed synchronous disposal
Add extension methods to run guaranteed synchronous disposal

Intended to be a temporary resolution to cases we need to ensure
components are disposed on the update thread. Should be used from
methods like `Screen.OnExiting` to force immediate cleanup of a child
drawable.

ppy/osu-framework,peppy/osu-framework,smoogipooo/osu-framework,ZLima12/osu-framework,ppy/osu-framework,smoogipooo/osu-framework,ppy/osu-framework,ZLima12/osu-framework,peppy/osu-framework,peppy/osu-framework