Add support for spawning multiple service processes

Modify activity manager code to allow for multiple processes to be
spawned for the same service (non-isolated) having different instance
names. A new API is introduced similar to bindService where the app UID
associated with the supplemental process service is used as the instance
name.

The main changes involve distinguishing it from isolated service
processes with instance name, removing a check that allows only isolated
services to have instance names and using distinguishing process names
in the ServiceRecord for the different processes running that service.

Bug: 203670795
Bug: 209058402
Test: Manual, installing two Supplemental client apps and attempting to
load code from each and examining new processes created. Automated tests
are WIP.

Change-Id: I2e349412338e6f0cc9cabaefb77fe2413f5850e0