Bypass telecom sequencing for managed CSs for multiple Calls on the same PA

When there are multiple calls on the same PhoneAccount for a managed
ConnectionService, leave it to the ConnectionService to handle sequencing
operations across those calls.

Fixes: 391452587
Flag: com.android.server.telecom.flags.enable_call_sequencing
Test: atest CtsTelecomCujTestCases; manual VZW multicalll tests
Change-Id: I87cdc3fb9fc3a34dec069fe0ee4d3547bd2c451f