Adjust formatting of accessibility guide link in Edit file and Pipeline editor
# Context
From https://gitlab.com/gitlab-org/gitlab/-/merge_requests/193026:
> The pipeline editor uses Monaco text editor. Monaco has some great a11y features built in, including a mechanism for escaping keyboard traps.
>
> The user is not made aware that it uses the Monaco text editor, so is not aware of the a11y features. This can lead to a user becoming keyboard trapped using the tab key.
https://gitlab.com/gitlab-org/gitlab/-/merge_requests/193026 added an `Editor accessibility guide` link to the Pipeline Editor. https://gitlab.com/gitlab-org/gitlab/-/merge_requests/218605 added an `Editor accessibility guide` link to the Source Code Edit single file view.
Other related issues:
* https://gitlab.com/gitlab-org/gitlab/-/merge_requests/217065+
* https://gitlab.com/gitlab-org/gitlab/-/issues/524739+
# Design proposal
The formatting and UX of this link could be improved.
1. Make the link open in a new tab, so users don't lose context or work while they are editing a file / pipeline.
2. Adjust the layout. Coordination with Pipelines designers needed. See https://gitlab.com/gitlab-org/gitlab/-/issues/585923#note_3003707286.
issue