GitLab Performance Monitoring is now able to track custom events not
directly related to application performance. These events include the
number of tags pushed, repositories created, builds registered, etc.

The use of these events is to get a better overview of how a GitLab
instance is used and how that may affect performance. For example, a
large number of Git pushes may have a negative impact on the underlying
storage engine.

Events are stored in the "events" measurement and are not prefixed with
"rails_" or "sidekiq_", this makes it easier to query events with the
same name triggered from different parts of the application. All events
being stored in the same measurement also makes it easier to downsample
data.

Currently the following events are tracked:

* Creating repositories
* Removing repositories
* Changing the default branch of a repository
* Pushing a new tag
* Removing an existing tag
* Pushing a commit (along with the branch being pushed to)
* Pushing a new branch
* Removing an existing branch
* Importing a repository (along with the URL we're importing)
* Forking a repository (along with the source/target path)
* CI builds registered (and when no build could be found)
* CI builds being updated
* Rails and Sidekiq exceptions

Fixes gitlab-org/gitlab-ce#13720

This change simplifies a Pipeline processing by introducing a special new status: created.
This status is used for all builds that are created for a pipeline.
We are then processing next stages and queueing some of the builds (created -> pending) or skipping them (created -> skipped).
This makes it possible to simplify and solve a few ordering problems with how previously builds were scheduled.
This also allows us to visualise a full pipeline (with created builds).

This also removes an after_touch used for updating a pipeline state parameters.
Right now in various places we explicitly call a reload_status! on pipeline to force it to be updated and saved.

Use fewer queries for CI charts

## What does this MR do?
It reduces number of queries sent for aggregating counts for CI graphs.

## Are there points in the code the reviewer needs to double check?
N/A

## Why was this MR needed?
For this project (gitlab-ce), loading `/graphs/master/ci` is so slow it times out eventually. I did a quick benchmarking on production and found that it can take 72.5 seconds to only load the controller action variables (there are queries done from the view, didn't look into those). This MR reduces the time to about 2.5 seconds.

Extra improvement could be done by introducing an index on `gl_project_id` and `created_at` for `ci_builds` table, but I can't confirm that right  now.

## What are the relevant issue numbers?
#20262 

## Screenshots (if relevant)
N/A

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- ~~[ ] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)~~
- ~~[ ] API support added~~
- ~~Tests~~
  - ~~[ ] Added for this feature/bug~~
  - [x] All builds are passing
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

See merge request !5502

* master: (321 commits)
  Fix the Sentry spam from CSP violations by disabling it.
  Limit git rev-list output count to one in forced push check
  Ensure Owners are included in the scope for authorized_projects
  Fix alignment of icons on project page
  Fix ci_status_helper_spec to look for new SVGs
  use 2.0.5, actually (2.0.4 was a bad release)
  upgrade rouge to 2.0.4
  Fix help page paths to make sure shortcuts and the UI help page work.
  fixes an issue cause by a bad merge
  Vertically align status icon within table
  Add new icons for every CI status
  Add global style for running icon
  Align running icon in merge request
  Add new running icon; add a bunch of styles to get svg to match existing fa icons
  Improve code design
  Fix broken builds_for_ref
  Move when tests before to make it no conflict with manual-actions
  Use value of `yaml_variables` and `when` from config_processor if undefined
  Add CHANGELOG entry
  CHANGELOG item
  ...

Conflicts:
	lib/ci/gitlab_ci_yaml_processor.rb
	spec/lib/ci/gitlab_ci_yaml_processor_spec.rb