This commit adds pipeline.type key to PipelineEntity.
This key will be used in MR widget in the next iteration.

The ref to the branch was being displayed as
raw HTML in the Pipelines page

Source branch can be removed after the merge and
we have to make sure to avoid rendering links if it's the case.

Commit changes

Add spec

Add changelog

fix

fix

Fix

Fix spec

Finish spec

ok

nice

ok

ok

ok

fix

In a few models we define ActiveRecord enums that are redefined in EE
using the following pattern:

    enum :some_enum, {
      ...
    }.merge(EE_ENUM_VALUES)

This particular approach is problematic to deal with, because it
requires that we `prepend` and EE module _before_ defining the enum.
This typically translates to the `prepend` being the first line in the
model in EE, but this can easily lead to merge conflicts when developers
add more `include` and/or `prepend` lines.

As part of https://gitlab.com/gitlab-org/gitlab-ee/issues/8244 and
https://gitlab.com/gitlab-org/gitlab-ee/issues/8241 we are moving
`prepend` to the last line in a file, reducing the chances of running
into merge conflicts. This poses a bit of a problem with the pattern
above, because this pattern does not allow us to move the `prepend`
further down a file.

To resolve this problem, we simply move the Hash value of the enum to a
separate class method. This method is defined in a separate module where
necessary, allowing us to use it like so:

    enum :failure_reasons, ::SomeModelEnums.failure_reasons

The method in turn is defined in a very straightforward manner:

    module SomeModelEnums
      def self.failure_reasons
        {
          ...
        }
      end
    end

This makes it easy for EE to add values without requiring the `prepend`
to be placed before the `enum` is defined.

For more information, see the following issues and merge requests:

* https://gitlab.com/gitlab-org/gitlab-ee/issues/8244
* https://gitlab.com/gitlab-org/gitlab-ee/issues/8241
* https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/8424

Enable frozen string in:

* app/presenters
* app/policies

Partially addresses #47424.

Conflicts:
	app/presenters/ci/pipeline_presenter.rb

Not only tracking auto-cancelling in pipelines,
we'll also track this in jobs because pipelines
could be retried and the information would get lost
when this happened. Also erase auto-cancelling
relation for pipelines when they're retried.