Add SipDelegateConnection#closeDialog

Add an API for IMS application to notify the SipDelegate when
to close the dialog and release all routing resources associated
with it.

Bug: 173833985
Test: atest CtsTelephonyTestCases:SipDelegateManagerTest
Change-Id: I7638c1d3a8e117f604a83ea241c5ec158f33a186