Transforms notes when the note was transformed in some other tab

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

This caused many pain points when working with it.
Part of the data was camel cased the other snake case.
Other parts where snake case & then getting converted in components,
this conversion has the potential for leaking memory.

This changes that & makes it consistent with what it returned from the
API, snake case.

Phil Hughes authored 6 years ago and André Luís committed 6 years ago

We now use the returned discussion instead of re-fetching
all of the discussions and filtering out the ones we don't need.
This speeds up the process of creating a diff discussions
by saving us another API request before we can render the discussion

`truncated_diff_lines` gets added to collapsed discussions when expanded
at this point `truncated_diff_lines` doesn't exist and is therefore not
reactive. This property gets added when creating discussions in order
for it to start as a reactive property

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

This reverts commit 9c121352, reversing
changes made to c1b335e0.

Discussions were being toggled by jquery DOM querying them and toggling
visibility but in vue, only the open discussions will be in the DOM
Fix includes:
 - Adds a getter to the store to get the expanded discussions
 - Adds an action to collapse a discussion
 - When the user clicks the button, all data needed is now accessible
   through a getter and we can dispatch an action to toggle the discussion
   within the state, instead of showing/hiding with jQuery
 - Removes hardcoded properties

Resolves #48237

This updates only the actual new discussion and not the full tree , which leads to a very costly full rerender

Closes #44099