[ADI][31/N] address API feedback on USER_RESPONSE_* constants

USER_RESPONSE_CANCEL and USER_RESPONSE_OK are pretty much the same from
the perspective of the installer. Thus combining them into a single
constant USER_RESPONSE_ABORT which indicates that the user has confirmed
to not to proceed with the installation because the developer
verification has failed or could not be completed.

FLAG: android.content.pm.verification_service

BUG: 422400021
FIXES: 422400021
BUG: 360129657
Test: CtsRootDeveloperVerificationPrivInstallerTarget36TestCases CtsRootDeveloperVerificationInstallerTarget36TestCases CtsRootDeveloperVerificationPrivInstallerTarget35TestCases CtsRootDeveloperVerificationInstallerTarget35TestCases CtsRootDeveloperVerificationVerifierTestCases

API-Coverage-Bug: 420966373

Change-Id: I1966a8e8e43961d17dd153aaaae1a15d5e4ca76b