Interworking between CallWaitingController and SsDomainController

If vendor Ims service handles the terminal based call waiting service
by itself, we should forward the request to Ims service as legacy
implementation when Ut is available. And SS_ROUTING_OVER_UT is replaced
with getSsRoutingOverUt() to check isUtEnabled().

Bug: 202463005
Bug: 202463163
Test: atest
Change-Id: I2d49916da09c733f949807577ac1dc55947cc31d
(cherry picked from commit 344d04ba6b5f529aa2405557a41b2184a2932c45)
Merged-In: I2d49916da09c733f949807577ac1dc55947cc31d