Adds Package check and TestApps test for PhoneAccount

1) Adds a check to ensure that a ConnectionService
is setting a PhoneAccount from the same Package name.

2) Adds TestApp test that switches PhoneAccount.

Bug: 27059146
Test: TestApp send intent to switch PhoneAccount
Change-Id: I5ac7dd8859d747b3aaaf5370af26a10225f8d6c2