Camera2: Refactor preview/recording management to separate class.

Untangle preview/recording management from main class to simplify
callpaths; in preparation for fixing several HAL/app interactions
bugs.

Bug: 7172543
Bug: 7159577
Bug: 7107220
Change-Id: Iab5503f66b35d88a1524111536a484c9e33fd934
7 files changed