Merge branch 'api-delete-note' into 'master'

Delete notes via API

Supports deleting issues, snippets, and merge requests via the API.

* Closes #14944
* Closes #14845 
* Closes #6060 

@zj I did not see that you assigned yourself in #6060. Hopefully, you did not start yet.

@rymai In #6060 this is targeted for 8.7 release. Could you review that and maybe this still lands in 8.7. 


See merge request !3557