Add simplified_network_settings_bool to CarrierConfig.

Some carriers want to further simplify network settings based on a
variety of wifi or cellular related bundles. Expose a config a
carrier might set to allow SysUi, Settings and platform to adjust.

BUG: 33111931
Test: runtest carrierconfig-unit
Change-Id: I35a7ef15bbba23cf9e0380432fc001804c7e1804
Merged-In: I35a7ef15bbba23cf9e0380432fc001804c7e1804