[10.x] Move ShouldBeUnique locking from PendingDispatch to Dispatcher

[meruiden]

When dispatching jobs through the dispatcher directly, the ShouldBeUnique logic isn't checked and the job won't be locked. This is strange undocumented behaviour imo and caused lots of bugs around our platform as we heavily rely on dependency injecting the Dispatcher class. I've seen other instances online where users also dispatch jobs directly on the Dispatcher and I feel like key logic like ShouldBeUnique should be implemented on this level as well as theres no added value to doing so on PendingDispatch level. This even feels kindof hacky to be implemented on PendingDispatch level.

[meruiden]

I realize now why it's hacked in at PendingDispatch level. It seems this is mostly to support the dispatchAfterResponse logic. But I still think there should be a workaround for this.

[taylorotwell]

Thanks for your pull request to Laravel!

Unfortunately, I'm going to delay merging this code for now. To preserve our ability to adequately maintain the framework, we need to be very careful regarding the amount of code we include.

If possible, please consider releasing your code as a package so that the community can still take advantage of your contributions!

If you feel absolutely certain that this code corrects a bug in the framework, please "@" mention me in a follow-up comment with further explanation so that GitHub will send me a notification of your response.