[MM-47489] Move Shared Channels (Experimental) to Professional (#21882)

* Move shared channels to professional license

* Remove references to SharedChannels from license and use license SKU instead

* add tests

* Refactor shared channels license check and add tests

* Re-add removed negation on license check

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

app/server.go

@@ -595,7 +595,7 @@ func (s *Server) startInterClusterServices(license *model.License) error {
 	// Shared Channels service
 
 	// License check
-	if !*license.Features.SharedChannels {
+	if !license.HasSharedChannels() {
 		mlog.Debug("License does not have shared channels enabled")
 		return nil
 	}