Add tests for mapIsolatedUidToHostUid methods

- Remove unneeded dependency on atoms.proto
- Remove extractIntoVector function. Assert on actual output directly.
- Use a helper method for creating UidMap mock for all tests.
- Add AttributionChain variants of existing tests in puller_util_tests.
- Add tests in StatsLogProcessor_test to test mapIsolatedUidToHostUid()
    in StatsLogProcessor.

Bug: 154285085
Test: bit statsd_test:*

Change-Id: I6d0822be9f0fbca23bd2f441dc63b97110567307