storaged: move proto file to /data/misc_ce/0/storaged

Use proto_stat to indicate status of CE area. Before user_0 unlocks,
storaged detects CE NOT_AVAILABLE when attempting to read the proto
file. It then skips reading/writting the proto.

When user_0 logs in, vold calls onUserStart in storaged, which sets
proto_stat to AVAILABLE. At next event, storaged tries to read the
proto. If it's a success, proto_stat is changed to LOADED. After that,
storaged reads and writes proto normally.

Test: adb shell storaged -u -p
Bug: 63740245
Change-Id: I1fdd42c430e91682f6cc07497fcad5be52489b4e