Pass $CI_COMMIT_TAG as GITLAB_TAG to the CNG triggered pipelines

See merge request gitlab-org/gitlab-ce!24639

(cherry picked from commit cc4b5656)

79eec047 Pass $CI_COMMIT_TAG as GITLAB_TAG to the CNG triggered pipelines

Improve the handling of tags and branches which contains a `/` when triggering CNG pipelines

See merge request gitlab-org/gitlab-ce!24465

(cherry picked from commit 16ab0050)

67dfd878 Use $CI_COMMIT_REF_SLUG in review-apps.sh
f8a10191 Use $CI_COMMIT_REF_NAME for tags in trigger-build

Optionally compiling assets when needed for qa jobs proved
unworkable so instead we fall back on compiling them for
all qa jobs.

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

The `gitlab:assets:compile` job isn't run for the QA branches, thus
there's no Docker image correspinding these branches in the registry.

By overriding `CI_COMMIT_REF_SLUG` to `master` for QA branches, the
`fetch-assets` job in the `omnibus-gitlab` pipeline will pull the
`master` assets Docker 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 the variable names consistent by following the
`TOP_UPSTREAM_SOURCE_*` pattern.
Signed-off-by: NRémy Coutable <remy@rymai.me>

This is needed because `GITLAB_VERSION` has a special meaning in
`omnibus-gitlab` triggers: this is the GitLab version to build.

The problem is that `omnibus-gitlab` also has triggers to run QA for an
`omnibus-gitlab` commit, and if we use `GITLAB_VERSION` in that case,
the comment would be posted on the GitLab CE/EE commit (stored in
`GITLAB_VERSION`), whci hwouldn't make any sense.
Thus we need `TOP_UPSTREAM_SOURCE_SHA` to represent the commit on
which we want to leave a comment.
Signed-off-by: NRémy Coutable <remy@rymai.me>

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

Refactor scripts/trigger-build and post a commit note with the downstream pipeline URL for omnibus triggers
Signed-off-by: NRémy Coutable <remy@rymai.me>

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

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