Update AgentV1DisconnectSession api signature

Will accept utils.CGREvent instead of utils.AttrDisconnectSession as a
parameter.

SessionSv1.ForceDisconnect will take utils.SessionFilterWithEvent as a
parameter instead of *utils.SessionFilter.

Added possibility to pass DisconnectCause as an Event parameter.

The forceSTerminate that's called when the session timer expires will
have DisconnectCause 'SESSION_TIMEOUT' instead of 'FORCED_DISCONNECT'.

Added Dispatcher methods for AlterSessions.

Event will be merged with EventStart of the session before being sent to
AgentV1DisconnectSession.

cmd/cgr-tester/sessions.go

@@ -34,13 +34,13 @@ import (
 
 var (
 	brpc             *birpc.BirpcClient
-	disconnectEvChan = make(chan *utils.AttrDisconnectSession, 1)
+	disconnectEvChan = make(chan utils.CGREvent, 1)
 )
 
 type smock struct{}
 
 func (*smock) DisconnectSession(ctx *context.Context,
-	args *utils.AttrDisconnectSession, reply *string) error {
+	args utils.CGREvent, reply *string) error {
 	disconnectEvChan <- args
 	*reply = utils.OK
 	return nil