Return UNSUPPORTED_ON_DEVICE in network/imei when no telephony

If the device does not have any telephony support (either via the
build-time config_show_sim_info=false boolean flag, or when not
declaring the PackageManager.FEATURE_TELEPHONY_DATA feature flag),
returning UNSUPPORTED_ON_DEVICE makes more sense than
CONDITIONALLY_UNAVAILABLE, as there is no runtime change that would
make it available.

This change also aligns the behavior with the deviceinfo/imei
entry.

Bug: 395714454
Flag: EXEMPT bugfix
Test: atest MobileNetworkImeiPreferenceControllerTest
Change-Id: Ia01cf3812f8343eabd8ea6970b691ac71432e8bd