This is needed because in `master`, the `gitlab:assets:compile` is
created, but not the `gitlab:assets:compile pull-cache` job, and the
`needs` keyword cannot take jobs that don't exist, thus we have to
create a dedicated job for `master`, with `needs: ["build-qa-image",
"gitlab:assets:compile"]` instead of `needs: ["build-qa-image",
"gitlab:assets:compile pull-cache"]`.
Signed-off-by: NRémy Coutable <remy@rymai.me>

This also makes 'package-and-qa-manual' created for 'master' because
it's a valid use-case to run manual QA on 'master'.

Without this change, no pipeline could be created for auto-deploy
branches due to the following error:

    The form contains the following error:
    package-and-qa-manual: needs 'build-qa-image'
Signed-off-by: NRémy Coutable <remy@rymai.me>

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

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

Make package-and-qa manual so the default `on_success` doesn't need
to be set on package-and-qa-always.

Remove unnecessary `except: []`

This commit adds CI job that validates all `*.yml`
with `yamllint`.

This commit fixes all offenses present in repository.

This way even if review-deploy failed we can still run it.

Ruby 2.6 offers better performance and memory usage:
https://www.rubyguides.com/2018/11/ruby-2-6-new-features/

Part of https://gitlab.com/gitlab-org/gitlab-ce/issues/57323

Also, play manual jobs once dependency jobs are done instead of polling
for the dependent jobs to be finished.
Signed-off-by: NRémy Coutable <remy@rymai.me>