Migrate puller registration to StatsManagerService

The code path to register and uregister pullers now goes through
StatsManagerService as opposed to StatsCompanionService. Pullers are
also now cached in StatsManagerService.

Test: m -j
Test: atest GtsStatsdHostTestCases (passes even when the RVC check is
removed from relevant tests)
Bug: 147010937
Change-Id: I6549a41e2059c5fc9e57d861b751760ef165f879