Support bindServiceAsUser in Telephony UT

This change introduces the support to call Context.bindServiceAsUser by
forwarding to Context.bindService.

In HSUM telephony, multiple components need to call bindServiceAsUser to
bind services in Main User from a system user's context. The change here
makes sure the existing UT cases wouldn't break.

Bug: 328251947
Test: atest FrameworksTelephonyTests
Flag: EXEMPT pure test case improvement
Change-Id: I6e9e7a98b5eae581dae12809c6e008f49425df2d