Replace invocation of `find` with Ruby code that matches old cached
files in a better, and safe way to avoid data-integrity issues.

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

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`.

This version of MySQL doesn't yet support 'LIMIT & IN/ALL/ANY/SOME
subquery'

Oh well.

https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/5347#note_13198105

https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/5347#note_13199055

So we no longer join anything, just find the latest pipeline
and load builds from there to avoid mixing builds.

Thanks Kamil for the help and tests.

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

also added a test for checking this.

Prior, when providing a `min_access_level` parameter to this method, we
called `Gitlab::Access.values` instead of `all_values`, mistakenly
omitting the `OWNER` level.

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/19878

https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/5347#note_13173842

https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/5347#note_13173871

Feedback:
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/5347#note_13170854

* This method previously iterated over all services in a project.  Now it
will directly query the ExternalWikiService for the project and filter
by active state.
* The presence of an external wiki is also cached
* When an external wiki is added or removed, the cached value is updated

This was extracted from !5142 and implementing part of #4255.
We split it from !5142 because we want to ship it in 8.10
while !5142 was not ready yet.

WIP - trying to replicate UTF-8 error

fix spec

fixing encoding issue and another spec, to do with MR diffs

fix issue and spec failure

Add changelog and bumped up I/E version

fix spec based on feedback - omitted target project

Refactor and rename `restricted_signup_domains` to `domain_whitelist` to better conform to its behavior and newly introduced behavior.