Extract internal GestureEffect out of ContentOverscrollEffect

This CL is extracting the internal GestureEffect and VisualEffect
classes out of ContentOverscrollEffect, because ContentOverscrollEffect
and OffsetOverscrollEffect are going to be moved to PlatformComposeCore
in ag/31063651.

Bug: 378470603
Test: N/A simple move
Flag: EXEMPT simple move
Change-Id: I1520254d250e798546461e4a411941ca82cff076