Use isMobileDataCapable/isVoiceCapable helpers in MainClear

Disabling telephony support may be done either with the
config_show_sim_info config option, or based on whether
TelephonyManager reports data capabilities. The isMobileDataCapable()
helper method ensures both ways are supported.

Additionally, the logic is also updated to explicitly check for voice
support, so that disabling this telephony element happens only when
both mobile data and voice are unsupported.

Bug: 395714454
Test: mm && atest
Flag: EXEMPT bugfix
Change-Id: I47d9ff41a73499cc7d705a9876352a258f97e53e