Add carrier config key to override Wi-Fi calling roaming mode.

When phone is connected to non-terrestrial network, carrier can specify
whether to override Wi-Fi calling roaming mode or not using
KEY_OVERRIDE_WFC_ROAMING_MODE_WHILE_USING_NTN_BOOL.

If KEY_OVERRIDE_WFC_ROAMING_MODE_WHILE_USING_NTN_BOOL is set to true,
then Wi-Fi calling roaming mode is set to Wi-Fi preferred.

Bug: 318871716
Test: atest CarrierConfigManagerTest, atest ImsManagerTest,
atest WifiCallingSettingsForSubTest
Test Request Bug: 320807503

Change-Id: I5f7a1c60b75cede92fd88366772802cc2b8795e1