Add a new UID range for SDK sandbox processes.

These are processes that are spawned alongside regular app processes.
They have their own UID range, such that they can be properly isolated
from applications.

Add some APIs in Process that allows the system and mainline
modules to verify that a particular UID belongs to a sandbox
process, and to map between the sandbox process and the
corresponding app process.

Bug: 215012578
Test: N/A
Change-Id: I02aaaa1c2bcf9d141ddc97747eb6d7edd52d7b92
Merged-In: I02aaaa1c2bcf9d141ddc97747eb6d7edd52d7b92