promote existing DO_NOT_LOG_CALL extra to @SystemApi

As a part of the mainline project, the DO_NOT_LOG_CALL extra
needs to be promoted to an @SystemApi since external processes
depend on it (wear).

This extra when injected into a call allows the call to skip the
call log. All backend logic has already been implemented. A new
CTS test has been added to assert the behavior.

Flag: com.android.server.telecom.flags.promote_extra_do_not_log_call_to_system_api
Bug: 427477225
Test: atest android.cts.telecom.IncomingCallTest#testDoNotLogCall
Change-Id: I26d87a7bf857d0a834ff2a504427d66925811349