Apply go/hc-page-token in the implementation

* Return full page token from RecordHelper and surface it up
  - Chain: RecordHelper -> TransactionManager ->
    HealthConnectServiceImpl
  - RecordHelper is where we calculate offset
  - Wrap everything is easier than bubbling everything up separately

* Add pageToken to ReadTransactionRequest
  - This allows the TransactionManager to access page token, and pass
    it on to RecordHelper

* BackupRestore is also changed, because there are two copies of the
  same code (in TransactionManager and BackupRestore)

* Extend test coverge
  - Unit test: RecordHelperTest
  - Integration test (cts): HealthConnectManagerTest

Test: atest HealthFitnessUnitTests
Test: atest HealthConnectManagerTest
Bug: 296846629
Change-Id: I48b1b58da8d9b94e57e6f492f8fa79cb9d7c9bab
10 files changed