WFC roaming mode setting can not be used with a fixed value

WFC roaming mode setting can not be used with a fixed value because it
is changed as WFC home mode changes if
KEY_EDITABLE_WFC_ROAMING_MODE_BOOL is false.

To solve this issue, separate the WFC mode setting of home and roaming.
These can switch behavior by new carrier config
KEY_USE_WFC_HOME_NETWORK_MODE_IN_ROAMING_NETWORK_BOOL.

Test: manual - Checked that WFC roaming mode is hidden if new config is
true.
Test: manual - Checked that WFC roaming mode is also changed when
change the WFC home mode if new config is true.
Test: auto - Passed WifiCallingSettingsForSubTest.
Bug: 79666081

Merged-In: Ib2363c5d50f5231cc89f287d760ca8728b02b249
Change-Id: Ib2363c5d50f5231cc89f287d760ca8728b02b249