storaged: split proto file into multiple CE areas

Use user_id (from app uid) to determine file location.
/data/misc_ce/<user_id>/storaged/storaged.proto

Vold notifies storaged when a user's CE area becomes available.
Then storaged restores data from the proto in that area and
combines them into IO history.

Vold also notifies storaged when the CE area is being deleted.
Storaged clears internal history about this user and deletes the
proto file.

IO perf is stored in user_0 area since it's not user related.

Test: dumpsys storaged before/after multiple users' unlock
Bug: 63740245
Change-Id: I39f923f6b09e9f2a29e9286ce02b3b3bcbfb9f94