Check ro.boot.radio.allow_mock_modem in USER build

Provide new ro.boot.radio.allow_mock_modem for emulator to set it,
so we have two property one is for developer options (persist.radio.*)
another is for emulator (ro.boot.*).

The setModemService is allowed in USER build as long as either is true.

Bug: 231323121
Test: emulator
Change-Id: I2904172265919770d9984605d27189b916d42b5b