[CDM perm sync] Fix user consent flow

Fix several issues in order to make the API CL clean. This CL doesn't
contain any API changes, but has been tested with the API changes.

1. Renamed isPermissionSyncAllPackages() to
   getPermissionSyncAllPackages() due to API convension.
2. Changed return type in the request store from List to ArrayList to
   fix a runtime expection that AbstractList can't add elements.

Bug: 213338076

Test: manually added and tested the user consent dialog flow in the CDM test app
Change-Id: Ibabb02e797f0ccf5288de976acfcc73ef6f67896