Enforce MODIFY_PHONE_STATE for TelecomManager system APIs.

Enforcing system-only permissions for TelecomManager APIs (see the bug
for rationale as to why some methods do not have the permission
enforced).

Test: Manual / GTS
Merged-In: I5a966e56da86d48892d917b02442ee7deffb39cb
Change-Id: I3f76602820c772b763f453a216d041454e3b94e6
Fixes: 62347125