optionally exclude threads in direct messages (#29042)

* optionally exclude threads in direct messages

* add excludeDirect option in client4

* Skip flaky test

* refactor double negate

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Co-authored-by: Mattermost Build <build@mattermost.com>

server/public/model/thread.go

@@ -88,6 +88,8 @@ type GetUserThreadsOpts struct {
 
 	// IncludeIsUrgent will return IsUrgent field as well to assert is the thread is urgent or not
 	IncludeIsUrgent bool
+
+	ExcludeDirect bool
 }
 
 func (o *Thread) Etag() string {