Create WifiCallingRepository

Move Wi-Fi calling related feature into it.

Which simplifies the ImsMmTelRepository, so we can put more
ImsMmTelManager related features into ImsMmTelRepository in the future
cl.

Bug: 325414275
Test: manual - on Mobile Settings
Test: unit tests
Change-Id: I391f43cfa3a79e0c44865050c357ac54346c2fb1