provideContextImage currently takes in taskId which works for the
Recents screen.
In Android QPR2 timeframe, content suggestions also powers Screenshots
feature which requires passing an explicit Bitmap.
This change adds a Bitmap parameter to the 'provideContextImage'.
Launcher/Recents will continue using the taskId-based API to obtain a
fresh snapshot using the Activity/Window Manager; or obtain an on-disk one for paused tasks.
Bug: 147324195
Test: atest ContentSuggestionsManagerTest
in separate CL ag/10146598
Change-Id: I686eb8d90a4a44fdd80403ef2df58020c82ca69a