Add "Enable Phone Account" CTS Verifier Test.

This CTS Verifier test ensures that a third-party ConnectionService can
register a phone account, and that the user is able to use the device's
"calling accounts" screen to enable the newly registered phone account.

Test: Manual / CTS Verifier
Bug: 36098357
Merged-In: I3a8a6465734c18487195c9cc13cf7aa2aa56f3ef
Change-Id: I3a8a6465734c18487195c9cc13cf7aa2aa56f3ef
(cherry picked from commit 405870e7d4fc38ebce7e6ebb0b07eb8610c5b842)
6 files changed