Fix Range Checking on registerTelephonyCallback

-Require that callbacks be registered with at least
 on valid event.
-Update the null checking to throw consistent NPEs
 as per the Android API Guidelines

Bug: 431293947
Test: atest TelephonyCallbackTest#testRegisterTelephonyCallback
Flag: EXEMPT bugfix
Change-Id: Id2d57f2078946bd163a82e6e4e3665c791adb788