Split appops.xml into two files

Currently AppOpsService persists appop state into a single "appops.xml"
file. Instead, split this file into two:

1. "appops.xml": stores appop state
2. "appops_accesses.xml": stores recent appop accesses

This allows us to split the responsibility of maintaining different
types of state across different services:

- app-op state: maintained by AppOpsServiceInterface (where the
  implementation can vary)
- app-op accesses: maintained by AppOpsService

For transition purposes, the app-op history will be read from the
original "appops.xml" file before the new file exists.

(Also, bring back the unrelated AppOpsCheckingServiceTracingDecorator
which was accidentally nuked in a recent change.)

Test: atest AppOpsUpgradeTest CtsAppOpsTestCases
Bug: 266163878
Change-Id: I1ffc6375abaf8c62f91e7aefe0b76923f437ee0e