Only set edge extension when fill_task or embedded_activity flag is set

Do not apply edge extensiion effect on letterboxed activity during
transition animation. Because the animation offset can be zero, check
bounds should be more reliable.

Flag: EXEMPT bugfix
Bug: 409896188
Test: verify no edge extension when opening activity in compat mode.
Test: atest ActivityTransitionTests
Change-Id: I931524f29c106997578725f32847f0531e356e93