add setDefaultExecutor to ImsCallSessionListener to set the executor when a conference call is established

add a way to set the executor variable in ImsCallSessionListener, because ImsCallSessionListener has the information of ImsCallSessionImpl, which passed from vendor

Bug: 262800764
Test: aTest android.telephony.ims.*
Test: Call / Conference call E2E regression test
Merged-In: I63ba6a9d4ea4b8d963bc7bc2ee8e1d019c75ee10
Change-Id: I63ba6a9d4ea4b8d963bc7bc2ee8e1d019c75ee10
3 files changed