Backport of Docs SEO: Update Configuration section to improve search into release/1.9.x

[hc-github-team-nomad-core]

Backport

This PR is auto-generated from #24759 to be assessed for backporting due to the inclusion of the label backport/1.9.x.

The below text is copied from the body of the original PR.

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Description

• Front matter description updates for DevDot search.
• Add intro body paragraph that summarizes page content ("This page..."). This is basically the same verbiage as the front matter description but in the body for better Google search indexing.
• Ensure front matter page_title and # <title> match.

I mostly did not edit page content because that's out of scope for this effort. I did some small replacements tho ("see", "below"). Added a few links to pages that didn't have any (orphan pages).

A member of the Runtime Education team will review all SEO PRs.

Links

Jira: CE-775
Preview: https://nomad-git-ce775-hashicorp.vercel.app/nomad/docs/configuration

Contributor Checklist

• Changelog Entry If this PR changes user-facing behavior, please generate and add a
  changelog entry using the make cl command.
• Testing Please add tests to cover any new functionality or to demonstrate bug fixes and
  ensure regressions will be caught.
• Documentation If the change impacts user-facing functionality such as the CLI, API, UI,
  and job configuration, please update the Nomad website documentation to reflect this. Refer to
  the website README for docs guidelines. Please also consider whether the
  change requires notes within the upgrade guide.

Reviewer Checklist

• Backport Labels Please add the correct backport labels as described by the internal
  backporting document.
• Commit Type Ensure the correct merge method is selected which should be "squash and merge"
  in the majority of situations. The main exceptions are long-lived feature branches or merges where
  history should be preserved.
• Enterprise PRs If this is an enterprise only PR, please add any required changelog entry
  within the public repository.

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Overview of commits

• ffb3431