Temporary decouple snapshot controller from transition.

- Accediently capture task snapshot when activity converting
  translucent.
- Need to fine tune the performance. When transition ready, only do
capture snapshot so it won't block surface placement. The other
analysis tasks such as load/remove/delete activity snapshot can be
schedule after transition finish. Also this version should only focus
on shell transiton.

Bug: 274216498
Test: manual test there won't capture snapshot when
app is converting from/to translucent.

Change-Id: I1c106dfd128d8ae229fbcba3ed1bd793dac36b67