Fix race conditions for AuthorizedProjectsWorker

Closes #26194 and #26310

See merge request !8701

Upgrade OmniAuth Ruby gem to 1.3.2

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/26813

See merge request !2056

Upgrade Brakeman to 3.4.1

Closes #26820

See merge request !8629

Revert "Merge branch 'switch-to-sassc' into 'master'"

Closes #26762

See merge request !8642

Switch to sassc-rails

Closes #18432

See merge request !8556

Closes #18432

This uses sassc to compile the application's SASS so it compiles faster.

Without attempting to be very scientific here are some numbers I got:

Using sassc-rails:

```
[1] pry(main)> Benchmark.bm { |bm| bm.report { Rails.application.assets["application.css"] } }
       user     system      total        real
   1.430000   0.380000   1.810000 (  1.830753)
```

Using sass-rails:
```
[1] pry(main)> Benchmark.bm { |bm| bm.report { Rails.application.assets["application.css"] } }
       user     system      total        real
  12.320000   0.530000  12.850000 ( 12.909684)
```

The result is faster page loads when changing CSS in development and
faster precompilation.

Remove rerun since it's not used anymore

Closes #19633

See merge request !8598

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

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

This MR enables rendering of PlantUML diagrams in Asciidoc documents. To add a
PlantUML diagram all we need is to include a plantuml block like:

```
[plantuml, id="myDiagram", width="100px", height="100px"]
--
bob -> alice : ping
alice -> bob : pong
--
```

The plantuml block is substituted by an HTML img element with *src* pointing to
an external PlantUML server.

This MR also add a PlantUML integration section to the Administrator -> Settings
page to configure the PlantUML rendering service and to enable/disable it.

Closes: #17603