We introduce ci_builds.environment_url and expand it when passing to
runners. In the future the deployment could also retrieve the URL from
the job instead of from the environment, which might have a different
external URL because of another deployment happened.

Use the EnforcedStyleForMultiline: no_comma option.
Signed-off-by: NRémy Coutable <remy@rymai.me>

This makes it possible to maintain backwards compatibility with configs
created when manual actions were non-blocking.

From now manual actions are blocking if configured with `allow_failure:
false`, otherwise manual actions are optional, and their status is
ignored.

This reverts commit e00fb2bdc2090e9cabeb1eb35a2672a882cc96e9.

# Conflicts:
#	.rubocop.yml
#	.rubocop_todo.yml
#	lib/gitlab/ci/config/entry/global.rb
#	lib/gitlab/ci/config/entry/jobs.rb
#	spec/lib/gitlab/ci/config/entry/factory_spec.rb
#	spec/lib/gitlab/ci/config/entry/global_spec.rb
#	spec/lib/gitlab/ci/config/entry/job_spec.rb
#	spec/lib/gitlab/ci/status/build/factory_spec.rb
#	spec/lib/gitlab/incoming_email_spec.rb

This reverts commit cb10b725c8929b8b4460f89c9d96c773af39ba6b.

Instead of using:
`coverage: /\(\d+.\d+%\) covered/`

This structure must be used now:
```
coverage:
  output_filter: /\(\d+.\d+%\) covered/`
```

The surrounding '/' is optional.

This commit:
* Turns `coverage_regex` into `coverage` entry in yml file
* Fixes smaller requests from code reviewers for the previous commit
* This commit is temporary (will be squashed afterwards)

This commit does not (further commits will do though):
* Add global `coverage` entry handling in yml file as suggested by Grzegorz
* Add specs
* Create changelog
* Create docs

* Instead of using the proposed `coverage` key, this expects `coverage_regex`

Feedback:
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/8088#note_20235080

So that this would be more consistent with the other variables,
which all of them are string based.

Closes #25554