Enable Carrier-Config cache for Settings

- Since the "Mobile-Data Details Settings" (NETWORK_OPERATOR_SETTINGS) will query Carrier-Config around 70 times during launching, use the Carrier-Config cache to reduce 69 times to speed up the launching time.

- It takes about 3ms to query a Carrier-Config each time.

- Create a singleton class to share the Carrier-Config for all
sub-settings.

Bug: 204135235
Test: manual test
atest -c ApnPreferenceControllerTest \
         AutoSelectPreferenceControllerTest \
         BackupCallingPreferenceControllerTest \
         CarrierConfigCacheTest \
         CarrierPreferenceControllerTest \
         CarrierSettingsVersionPreferenceControllerTest \
         DataServiceSetupPreferenceControllerTest \
         Enable2gPreferenceControllerTest \
         EnabledNetworkModePreferenceControllerTest \
         Enhanced4gBasePreferenceControllerTest \
         MobileNetworkUtilsTest \
         NetworkProviderBackupCallingGroupTest \
         NrAdvancedCallingPreferenceControllerTest \
         PreferredNetworkModePreferenceControllerTest \
         TelephonyTogglePreferenceControllerTest \
         WifiPickerTrackerHelperTest
make RunSettingsRoboTests \
     ROBOTEST_FILTER=ContactDiscoveryPreferenceControllerTest
make RunSettingsRoboTests \
     ROBOTEST_FILTER=VideoCallingPreferenceControllerTest

Change-Id: I26f9ac115a754910b5d59e820703f1a0e701bb7f