Transforms notes when the note was transformed in some other tab

Signed-off-by: Takuya Noguchi <takninnovationresearch@gmail.com>

When converting a comment to a discussion
if the "Cancel" button is used to exit the new discussion note,
the comment would revert back to its initial state

Sets `updated_at` so that the transformed note is returned together with
the new reply

Before, diff file `higlighted_diff_lines`/`parallel_diff_lines` and
diff discussion `truncated_diff_lines` were inconsistent: `text` and
`rich_text` on the latter included the leading +/-/<space> character,
like on the backend, while the former had no `text` and its `rich_text`
had dropped this char.

This resulted in a bug when the suggestions feature expected these diff
line objects to be identical in format and thus interchangeable, which
was not the case.

**What was the issue?**
Notes can be unresolved, but not resolvable. Without this, the
unresolvedDiscussionsCount was inflated.

**References**
https://gitlab.com/gitlab-org/gitlab-ce/issues/55138

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/53600

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

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/51370