This commit adds a helper text that describes what will happen when a
user clicks the "Start/Add to merge train when pipeline succeeds"
button.  This text appears at the bottom of the merge request widget.

In addition, this commit renames the "merge_train_info" component to
"merge_train_position_indicator" to avoid ambiguity with the
"merge_train_helper_text" component.

A recent change within gitlab-ui introduced a new size (24x24)
and changed also some of the existing sizes.

This commit uses the loading-icon's new size (24x24) to bring it to the
same dimensions as the status-icon and applies some styling to
vertically align them.

This reverts commit c3751046d217008404a0bd371e59d6ffd6734923.

Align icons left
Align text left
Adjust padding to be consistent
Make icons same 24 size
Add changelog mr number
Add right margin to widget status container
Add left margin inside widget icon container
Prepend left padding for error message
Only give button left margin, some have buttons
Prettify
Adjust test summary icons
Prettify
Fix empty line before lint
Remove author
Switch to use gl-padding
Use utility classes instead
Prettify
Change loading icon size to md
Update summary_row.vue

This commit adds an informational message under the pipeline block in
the merge request widget that displays the current position of the merge
request on the merge train.

- Makes activity dropdown and resolved counter smaller
- Uses grid for spacing
- Removes scrolling on MR tabs

It does this by removing the `.accept-control` class which
was only causing problems.

Adds backport changes for ee

Align elements horizontally and add missing bottom padding

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

- Compare versions header is full width except in the unified diff mode
with no tree sidebar
  - Bar is always full width, but the content within stays centered when
unified and no tree sidebar
- File header is the same height as the "Compare versions header"
- aligns with the design system grid guidelines => 56px
- Diff file headers use a button group, switch icon order to open file
externally being the last option, all buttons will become icon buttons
(icon delivery by @dimitrieh)
- If a file header becomes sticky no rounded corner/double border
problem is visible anymore

Introduces a new status for builds between :created and :pending
that will be used when builds require one or more prerequisite
actions to be completed before being picked up by a runner
(such as creating Kubernetes resources before deploying).

The existing :created > :pending transition is unchanged, so
only builds that require preparation will use the :preparing
status.

This commit lowers the z-index of the .merge-request-tabs-holder class
to avoid rendering conflicts with the mini pipeline status dropdown
on the merge request page.

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/57691

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/58625

Added stylelint to static-analysis
Updated yarn dependencies
CSS Fixes and rule adoptions of stylelint
Added stylelint-scss
Deduplicated yarn.lock to clear dependencies

First round of advanced stylelint rules

Mainly Vendor prefix updates related to flex

Updates to more webkit specific vendor prefixes

Finished all vendor specific fixes

Moved now 4 rules to warning

Fixed the new scss lint problems

More stylelint adaptions after rebase

This class is used in:

- `group_test_reports_app.vue` where the padding is overruled by
  `.mr-report`
- `mr_widget_options.vue` where the padding is overruled by `p-0`
- `ee/mr_widget_options.vue` where there is a bug because the padding
  is not overruled.

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/51857

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/53304

- https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/8593
- Create mr-widget-icon to encapsulate circle icons
- Decouple workflow L&F from mr-widget-heading
- Decouple container L&F from mr-widget-heading

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/53019

In the Merge Request widget, the reports for tests
had an extra border.
The loading icon in the mr widget used in all
report sections had an extra margin causing text
to be misaligned.
This commit fixes both issues

Closes #52147

This file tree displays all the diff files in a tree like format
Each file is taken and converted into a tree with folders
Each folder can be toggled open & closed
Clicking a file will scroll to the diff file & highlight with a glow affect

Searching the tree list will search only files & return a list of the
files without any folders

Each file row contains an icon to show changed, new file or deleted
Each row will also contain the added & removed lines count

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/14249