Merge Trampoline and BMS

Perform the merge by:
1. Moving lifecycle inside Trampoline without IDE support
(since we'll rename Trampoline in this CL as well, making the published binder
the same).
2. Move constants to Trampoline without IDE support as well (again, we'll
rename Trampoline).
3. Change the last usages of BMS constructor to use
Trampoline's. Now BMS is effectively empty.
4. Delete BMS.
5. Rename Trampoline to BMS with IDE support (renaming related classes
and variables that the IDE could find).
6. \o/

Split CL into Path Sets to ease review:
Base > PS2: Steps 1..4 (+121 -333)
PS2 > PS4: Step 5 (+214 -204)

Test: m -j
Test: adb shell dumpsys backup
Test: atest BackupManagerServiceTest BackupManagerServiceRoboTest
Bug: 135661048
Change-Id: Ia6cd340d3c5fcdb9c8f409035d032efeb090cd20