The method Ability.issues_readable_by_user takes a list of users and an
optional user and returns an Array of issues readable by said user. This
method in turn is used by
Banzai::ReferenceParser::IssueParser#nodes_visible_to_user so this
method no longer needs to get all the available abilities just to check
if a user has the "read_issue" ability.

To test this I benchmarked an issue with 222 comments on my development
environment. Using these changes the time spent in nodes_visible_to_user
was reduced from around 120 ms to around 40 ms.

Currently, even when searching for all authorized issues of *one* project, we run the
`Users#authorized_projects` query (which can be rather slow). This update checks if
we are handling issues of just one project and does the authorization check locally.
It does have the downside of basically repeating the logic of `Users#authorized_projects`
on `Project#authorized_for_user`.

There are several changes to this module:

1. The use of an explicit stack in Participable#participants
2. Proc behaviour has been changed
3. Batch permissions checking

== Explicit Stack

Participable#participants no longer uses recursion to process "self" and
all child objects, instead it uses an Array and processes objects in
breadth-first order. This allows us to for example create a single
Gitlab::ReferenceExtractor instance and pass this to any Procs. Re-using
a ReferenceExtractor removes the need for running potentially many SQL
queries every time a Proc is called on a new object.

== Proc Behaviour Changed

Previously a Proc in Participable was expected to return an Array of
User instances. This has been changed and instead it's now expected that
a Proc modifies the Gitlab::ReferenceExtractor passed to it. The return
value of the Proc is ignored.

== Permissions Checking

The method Participable#participants uses
Ability.users_that_can_read_project to check if the returned users have
access to the project of "self" _without_ running multiple SQL queries
for every user.

Also removes the note from the development/testing.md guide

In 8278b763d96ef10c6494409b18b7eb541463af29 the default behaviour of annotation
has changes, which was causing a lot of noise in diffs. We decided in #17382
that it is better to get rid of the whole annotate gem, and instead let people
look at schema.rb for the columns in a table.

Fixes: #17382