Allow passing the bitmap to ContentSuggestionsService via the extras Bundle

This change creates a constant in ContentSuggestionsManager, which will
be used to pass a hardware bitmap to ContentSuggestionsService.
In the presence of this key in the request extras, we skip taking a
snapshot in ContentSuggestionsPerUserService.
Bitmap is extracted from reading this value from extras in
ContentSuggestionsService.

Test: Manually tested this code in the debugger to verify that snapshot
is not taken when constant is provided in extras.

Change-Id: I4a464d5188bd3eac9afb4ac223611dccab01510f