It was a good decision in hindsight to keep the public module as 0.x
because this would have been a breaking change again.
https://mattermost.atlassian.net/browse/MM-53032
```release-note
Changed the Go module path from github.com/mattermost/mattermost-server/server/v8 to github.com/mattermost/mattermost/server/v8.
For the public facing module, it's path is also changed from github.com/mattermost/mattermost-server/server/public to github.com/mattermost/mattermost/server/public
```
* Migrate all method in model/client4.go to accept a context.Context
* Fix th.*Client
* Fix remaining issues
* Empty commit to triger CI
* Fix test
* Add cancellation test
* Test that returned error is context.Canceled
* Fix bad merge
* Update mmctl code
---------
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