Because the UI changed.
Related to: https://gitlab.com/gitlab-org/gitlab/-/issues/366082/

Page edits and link updates

Changelog: changed

Closes https://gitlab.com/gitlab-org/gitlab/-/issues/300479

When creating a merge request, the behaviour of the prefilled title and
discription is different than the behaviour of squashed commit messages.

For squashed commit messages, the behaviour is described in the
[docs](https://docs.gitlab.com/ee/user/project/merge_requests/squash_and_merge.html#overview)
as

> Taken from the first multi-line commit message in the merge.

However, for merge requests, the current behavior is to use the branch
name.  This commit sets the prefilled MR title/description to the first
multi-line commit in the MR, if applicable.  Otherwise falling back to
the previous behaviour.

These pages were all part of the Source Code group, but I believe
they should be reassigned to the new(-ish) Code Review group.

Add a preliminary  **(FREE)** badge to the H1 line for each of these
pages. While these badges may not be correct, it will give the PMs an
opportunity to review the badging and correct it if needed.

For the new tier name changes
https://gitlab.com/gitlab-org/technical-writing/-/issues/344

Related to: https://gitlab.com/gitlab-org/gitlab/-/issues/291023

The previous URL had two drawbacks:

1. It didn't match what the title was about (`Assignments to DevOps
   Stages and Groups`, and the anchor was `#designated-technical-writers`).
2. It didn't account for the other sections, like development and API
   guidelines.

- Files: merge-requests/*
- Stage: Create
- Group: Source Code

Fix more spelling errors when warranted, and update the exceptions
list when the words are real ones.

Fix words that are repeated, as detected by
Vale repetition test

The URLs needs hyphens now, so did a find and
replace to add them.

Find and replace bash with shell

The following pages had spelling errors, or code that was not
wrapped in inline code tags, which triggered spelling errors:

- doc/user/project/integrations/prometheus_library/cloudwatch.md
- doc/user/project/issues/csv_export.md
- doc/user/project/merge_requests/creating_merge_requests.md
- doc/user/project/merge_requests/merge_when_pipeline_succeeds.md
- doc/user/project/repository/forking_workflow.md
- doc/user/project/web_ide/index.md
- doc/user/project/clusters/serverless/aws.md

After performing automated spell checks across the entire docset,
this merge request corrects many spelling errors across the
documentation.

- Create a new document for introduction to MRs
- Document all the ways to create a MR
- Move content accordingly

Update docs and screenshot

Fix old content and improve structure, and remove
repetition. Also brings back content deleted by accident

Move several features from create MR doc to
review MR doc. Also splits security reports into
it's own section, to allow for one ULTIMATE badge

Fix links to moved content, and add front matter
to new files.

Continued work on creating_merge_requests.md
by adding section for important basic details
on the workflow, and adding/removing links
and sections as necessary. Drastically simplifies
documentation for MRs.

Split docs into an index, a create MR doc, and a review MR
doc. [ci skip]