Run full vale and markdownlint for docs pipeline changes

What does this MR do?

This tries to prevent broken masters caused by MRs like: !87981 (merged)

In this case:

• The pipeline passed for the MR: https://gitlab.com/gitlab-org/gitlab/-/jobs/2478965737
• The pipeline failed when it hit master: https://gitlab.com/gitlab-org/gitlab/-/jobs/2479693648

The key details is in the first pipeline:

Merged results pipeline detected. Testing only the following files:
doc/raketasks/sidekiq_job_migration.md

When running merged results pipelines, we normally only lint the changed files because it speeds up the job 10x. In a few cases, we want to always run on ALL docs, such as when we change the linting configuration or script. The part we were missing was that we also want to lint ALL docs when we change the docs pipeline configuration too. So, this MR:

• Changes the pipeline so that docs linting jobs run when the docs pipeline configuration is changed.
• Changes the script so that ALL docs are linted when the pipeline configuration is changed.

Related issues

Checklist

Pre-merge

Consider the effect of the changes in this merge request on the following:

• Different pipeline types
• Non-canonical projects:
  • gitlab-foss
  • security
  • dev
  • personal forks
• Pipeline performance

If new jobs are added:

• Change-related rules (e.g. frontend/backend/database file changes): _____
• Frequency they are running (MRs, main branch, nightly, bi-hourly): _____
• Add a duration chart to https://app.periscopedata.com/app/gitlab/652085/Engineering-Productivity---Pipeline-Build-Durations if there are new jobs added to merge request pipelines

This will help keep track of expected cost increases to the GitLab project average pipeline cost per merge request RPI

Post-merge

• Consider communicating these changes to the broader team following the communication guideline for pipeline changes