Check system process UID with a multi-user-aware way

This CL calls UserHandle.getAppId to compare system process UIDs
with Process.XXX_UID constants which are app id instead of UID in
multiple user context.

Bug: 328511085
Test: atest CtsWebkitTestCases
Flag: com.android.internal.telephony.flags.support_phone_uid_check_for_multiuser
Change-Id: Icc0f3ed6c7e6de868c88b13e3b38996c9193a8b8