Only prometheus can be uninstalled atm, the rest will be dealt with
later.

Presumption is that new application types will have uninstallation
implmemented at the same time.

In Rails 5, including `ActionView::Context` can have a significant and
hidden performance penalty because this module also includes
`ActionView::CompiledTemplates`. This means that any module that
includes ActionView::Context becomes a descendant of
`CompiledTemplates`.

When a partial is rendered for the first time, it runs
`ActionView::CompiledTemplates#module_eval`, which will evaluate a
string that defines a new method for that partial. For example, the
source of partial might be this string:

```
def _app_views_project_show_html_haml___12345(local_assigns, output)
  "hello world"
end
```

When this string is evaluated, the Ruby interpreter will define the
method and clear the global method cache for all descendants of
`ActionView::CompiledTemplates`. Previous to this change, we
inadvertently made a number of modules fall into this category:

* GroupChildEntity
* NoteUserEntity
* Notify
* MergeRequestUserEntity
* AnalyticsCommitEntity
* CommitEntity
* UserEntity
* Kaminari::Helpers::Paginator
* CurrentUserEntity
* ActionView::Base
* ActionDispatch::DebugExceptions::DebugView
* MarkupHelper
* MergeRequestPresenter

After this change:

* Kaminari::Helpers::Paginator
* ActionView::Base
* ActionDispatch::DebugExceptions::DebugView

Each time a partial is rendered for the first time, all methods for
those modules will have to be redefined. This can exact a significant
performance penalty.

How bad is this penalty? Using the following benchmark script, we can
use DTrace to sample the Ruby interpreter:

```
Benchmark.bm do |x|
  x.report do
    1000.times do
      ActionView::CompiledTemplates.module_eval("def testme\nend")
    end
  end
end
```

This revealed a 11x jump in the time spent in `core#define_method`
alone.

Rails 6 fixes this behavior by moving the `include CompiledTemplates`
into ActionView::Base so that including `ActionView::Context` doesn't
quietly affect other modules in this way.

Closes https://gitlab.com/gitlab-org/gitlab-ee/issues/11198

Update merge request widget to accommodate post-merge pipelines

See merge request gitlab-org/gitlab-ce!25983

This commit adds two new warning messages to the MR widget that handle
cases involving merge request pipelines.

Add time tracking progress bar to Issue Boards sidebar.

Extract preloaded_relations

See merge request gitlab-org/gitlab-ce!27168

Backports https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/10161
(code out of ee/ folder).