Fix usages of PackageManager APIs in Telephony

Remove usages of the hidden PackageManager#*asUser methods from
Telephony, and add some unit tests to verify the functionality.

Test: atest FrameworksTelephonyTests
Test: atest TelephonyCommonTests
Bug: 146834818
Change-Id: I2e2ec2c421773e3ff58556373896238e1ff0678a