Support new APIs in TelephonyManager to set/clear signal update request

Introduce set/clearSignalStrengthUpdateRequest in TelephonyManager
and ITelephony to support customized signal request from applications.

Bug: 164432835
Test: atest android.telephony.cts.TelephonyManagerTest
Change-Id: I749376872915a91b9514884547140eaf969dba0e