Uid Sandboxing of Pullers

Overall flow of implementation:
1. parsing the config in MetricsManager to store the uids per atom. It
follows the mAllowedLogSources logic very closely
2. MetricsManager register itself as a PullUidProvider with the
PullerManager.
3. Metrics pass the config key when pulling (for both registering
receivers and normal pulls) , and the puller manager gets
the allowed uids from the PullUidProvider for that config.
4. PullerManager keys receivers by <atomId, configKey> so that it can
look up the uids for that atom using the PullUidProvider as well.
5. Added shell subscriber support. Hardcode a default of AID_SYSTEM for
them and also allow packages per atom. This involved adding a second
interface to Pull that simply accepts the uids, since I didnt want to
make the ShellSubscriber a PullUidProvider as well.
6. Change adb shell cmd stats pull-source to allow users to specify a
package. Default to AID_SYSTEM as well.

Notes:
The feature is flagged off right now, since configs do not pass in the
desired package. Another approach could be to hardcode in the current
mapping, but that doesn't work for OEM pulled atoms.

Test: m statsd
Test: bit statsd_test:* with useUids = false
Test: bit statsd_test:* with useUids = true
Bug: 144099783
Bug: 151978258

Change-Id: I4a7481d7402a52b9beb4ea28b102803f9e50e79f