Internal: make sure that all delete mapping internal requests share the same original headers and context

Delete mapping executes flush, delete by query and refresh operations internally. Those internal requests are now initialized by passing in the original delete mapping request so that its headers and request context are kept around.

Closes #7736
Internal: make sure that update internal requests share the same original headers and request context

Update request internally executes index and delete operations. We need to make sure that those internal operations hold the same headers and context as the original update request. Achieved via copy constructors that accept the current request and the original request.

Closes #7766