Improve the renderign of new and existing discussions
by reducing the number of watchers on each object & array.
Previously every discussion change would trigger an update for every
discussion component.

Also tidied up some components to get them closer to our docs.

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/51506

Pre-request to https://gitlab.com/gitlab-org/gitlab-ce/issues/48956

Display `formatter` as the sole content of `position` object.
This means `diff_file` data is not referenced, which is the
caseu of "IOError: not opened for reading".

This reverts commit e0fe97ca4a506405af8e85368f2c69cda637e192.

This reverts commit 740ae2d1, reversing
changes made to 1ba47de5.

This reverts commit ced005f3, reversing
changes made to 9b01b293.

Add loading button for better UX

Adds back missing CSS class that was breaking tests

[ci skip] Add issue data and notes data provided through haml to the store to stop querying the DOM everywhere