[ADI][4/N] APIs for verification policy and failure reasons

+ Define failure reason codes
+ Define policy constants
+ Removed VERIFICATION_FAILED_REASON_NETWORK_LIMITED
+ Add getter/setter for session and global policy overrides
+ Allow Shell to have VERIFICATION_AGENT permission

FLAG: android.content.pm.verification_service

BUG: 360129103
BUG: 360129657

Test: cts tests to be added
API-Coverage-Bug: 367776952

Reverted changes: /q/submissionid:30469933-revert_verification_service_main

Merged-In: I64db0060656548b036a013d8265b52cb5c9bd1cf
Change-Id: I64db0060656548b036a013d8265b52cb5c9bd1cf