totalNotes is only used to prerender a number of
skeleton containers until real notes are loaded

issuable.discussions makes multiple requests, so
too expensive for this

This commit uses mere notes for this and sends
actual totalNotes number if it's less than 10;
otherwise it sends 10 - it allows us to avoid
bunch of skeleton prerenderings, which are not
necessary since they doesn't fit into the whole
screen and disappear quite fast

This is now entirely handled by `create_note`:

1. Project snippets prevent `create_note`.
2. Uploads already only support routing for personal snippets.

This simplifies some policies and access checks, too!

This style change enforces `return if ...` instead of
`return nil if ...` to save maintainers a few minor review points

This engine was replaced with CommonMarker in 11.4, it was deprecated
since then.

Add commit prop to NoteableNote component and pass it from
NoteableDiscussion

This reverts merge request !23622

Partially addresses #47424.

Closes #44099

There are several quick actions now that don't need this access - /todo and
/unsubscribe for instance - but when these were first added, there
weren't. Quick actions are now responsible for checking their own permissions.

this will remove the need make N queries (per-note) at the
cost of having to mark notes with an attribute

this opens up the possibility for other special roles for notes

a new badge will be added when an user that doesn't yet
have any merged merge request is discussing on either issues or
merge requests that he created.

this is indented for people to use extra care when discussing with
a new contributor.

A commit comment shows in the MR, but if the MR is from a fork, it will have a
different project ID to the MR's target project. In that case, add an
note_project_id param so that we can pick the correct project for the note.

This commit moves the rendering of the button back to the server, and
shows/hides it using opacity rather than display. It also removes the
transform applied to the button on hover (scale). Previously, both of these
factors automatically triggered a reflow, which creates a performance
bottleneck on pages with larger DOM size.

MR: !12103

Fix https://gitlab.com/gitlab-org/gitlab-ce/issues/27070

Deprecate "chat commands" in favor of "slash commands"

We looked for things like:

 - `slash commmand`
 - `slash_command`
 - `slash-command`
 - `SlashCommand`

Use the EnforcedStyleForMultiline: no_comma option.

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