Use 'file' query param instead of 'pin'

Updates the logic of the show/hide all comments action to include toggling
diff file discussions.
Added a new expansion component to collapsed diff file discussions.

https://gitlab.com/gitlab-org/gitlab/-/issues/465457

Now collapse\expand all unresolved threads will always
show or hide comments on the Changes tab in merge request

Changelog: changed

This allows users to comment on the full diff file instead of
only being allowed to comment on a line in a diff file.

In preparation for single-file-only file-by-file review,
the UI must always refer to the FULL list of files for
identifying order, finding files by hash, total number of
files, and more. Since `diffFiles` could be empty, `diffFilesMeta`
is the authority on these meta-values.

https://gitlab.com/gitlab-org/gitlab/-/merge_requests/58833 was merged,
but broke some FOSS specs because the code was moved to `ee/` while
the corresponding specs were not moved.

This reverts merge request !58833

... when getting the default suggestion commit message

See https://gitlab.com/gitlab-org/frontend/eslint-plugin/-/issues/18
for more information.

Big wins:
 - Not hooked into the Vuex sequence / memory load
 - Results aren't cached!!

Mandatory not to break master. Automatically created with prettier.

Also adds a getter to sort the reviews into
an array organized in the same order as
diffFiles.

Of course, this means that there's a bunch of logic
to coordinate the new flag with the original -
`automaticallyCollapsed` - flag.

In addition: the UI is updated to use the new flag
whenever it's been set, but to continue to fall back
to the old flag. This is primarily facilitated by a new
helper utility for diff files to do the resolution in a
single centralized place.

Of note: the diff_file is updated to depend on the
global store as the authoritative source of determining
whether the file is collapsed or not. The previous
version kept a local `isCollapsed` in sync with the
global store, which introduced a huge amount of
interwoven complexity. The update ingests the
resolved collapsed state from the store when
various observed properties update instead of
inverting that flow.

This is a full refactor of file collapsing.
Because the previous version was a single flag, then
modified with a user preference (file-by-file), there
were some issues including a THIRD possible way
that collapsing works. This update slightly simplifies
how collapsing works by depending more heavily
on the two flags stored in state and only modifying
them with the user preference when necessary.

- This leaves a small inaccuracy since now the "manual" (user) collapsed
    files are toggling the "automatic" flag. This will be resolved in an
    upcoming merge request.

Cleans up the diff header by moving the action buttons
into a more actions dropdown.

Closes https://gitlab.com/gitlab-org/gitlab/-/issues/199725

See https://gitlab.com/gitlab-org/gitlab/-/issues/202172

This is part of multiple merge requests in order to reduce the risk of
breaking master

Signed-off-by: Rémy Coutable <remy@rymai.me>

Update actions to return data
Remove diffFilesLength getter
Use local state and props for diffFilesLength
Update tests

Mousetrap is used as the help-tool to listen to keystrokes

Added currentDiffIndex getter to store that holds
the index of currently active diff file in the list

Instead of computing it on the component, we will take advantage of it
being available for all components in DiffsApp

Testing keyboard navigation and jumpToFile()

- replaced file.too_large
- replaced file.text
- replaced file.collapsed

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/53304

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/54807

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.

This restores the behaviour of showing the expand all button on diffs
even when only a single file is collapsed.
Previously the button would only show when all files are collapsed.

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/51737

This file tree displays all the diff files in a tree like format
Each file is taken and converted into a tree with folders
Each folder can be toggled open & closed
Clicking a file will scroll to the diff file & highlight with a glow affect

Searching the tree list will search only files & return a list of the
files without any folders

Each file row contains an icon to show changed, new file or deleted
Each row will also contain the added & removed lines count

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/14249