Adds Job specific variables to facilitate specifying variables when
running manual jobs.

This MR updates the y_label values and the label
values in common_metrics and cluster_metrics to
append the units of measurement to the labels.

Adds event enum column to DesignsVersions join table

See merge request gitlab-org/gitlab-ce!30745

It needs to default to an empty array logically.

`Array.reverse_each` is faster than `Array.reverse.each` because:

* reverse.each creates a new array then loops each element
* reverse_each loops in reverse order (no intermediate array created)

Backport of https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/14597

See merge request gitlab-org/gitlab-ce!30520

Also adds index to support scopes and queries

This supports https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/14656

* Limits raw requests to 300 per minute and per raw path.
* Add a new attribute to ApplicationSettings so user can change this
value on their instance.
* Uses Gitlab::ActionRateLimiter to limit the raw requests.
* Add a new method into ActionRateLimiter to log the event into auth.log

Related to https://gitlab.com/gitlab-org/gitlab-ce/issues/48717

Signed-off-by: Istvan szalai <istvan.szalai@savoirfairelinux.com>

This is the first part of Docker Registry replication
    for secondary Geo node.