Tethering: add isTetheringSupported with callerPkg parameter

BT tethering need to know whether tethering is supported for its caller
that call isTetheringSupported in binder thread under BT's process.
Current isTetheringSupported API is getting callerPkg inside
TetheringManager that would be BT's package name for bt tethering case.
Provide isTetheringSupported(String callerPkg) for caller to pass its
caller's package name if the use case is under binder IPC.

Bug: 146915889
Test: -boot, flash, boot

Change-Id: I01646fe045772c57b4e39a5e129531f8a2cea89f
Merged-In: I01646fe045772c57b4e39a5e129531f8a2cea89f
Merged-In: I2a35e1b6851e7a799c343be0dd60da23514768ba
(cherry picked from commit e09a92fa)