Backport of Docs: Community plugins section refactor into stable-website

[hc-github-team-nomad-core]

Backport

This PR is auto-generated from #25891 to be assessed for backporting due to the inclusion of the label backport/website.

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

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Description

Plugins > Community > Overview page and left navigation links to individual community-authored plugins.

We generally do not create and maintain content on how to use third-party plugins with our products. Much of the content related to Community-authored plugins is outdated, the plugin's own docs are more up-to-date, or the plugin is no longer maintained.

Plugin	Last Release Date
Lightrun	4/25
Pot	12/23
Pledge	11/23
Roblox containerd	5/23
systemd-nspawn	4/23
nomad_iis	3/23
Rookout	6/21
Firecracker	5/21
Roblox win_iis	4/20
Jail	6/19
Singularity	4/19

This PR does the following:

• Update Plugins > Community > Overview page to mention and point to the Integrations section.
• Change the community plugin left menu items to point to the plugin's external docs.
• Remove community plugin pages. These pages continue to exist in prior version branches (1.9, 1.8). Add redirects.

Approach approved by Jeff Boruszak, Matt McQuillan, and Austin Workman.

3 weeks ago I submitted PRs to rookout-nomad-driver, nomad-driver-nspawn, nomad-driver-iis, and nomad-driver-singularity repos. Those PRs still have not been reviewed, so my guess is that those plugins are no longer maintained.

Redirect Testing

• https://nomad-git-ce724-hashicorp.vercel.app/nomad/drivers/community/lightrun > https://docs.lightrun.com/integrations/nomad/
• https://nomad-git-ce724-hashicorp.vercel.app/nomad/drivers/community/pot > https://github.com/bsdpot/nomad-pot-driver
• https://nomad-git-ce724-hashicorp.vercel.app/nomad/drivers/community/pledge > https://github.com/shoenig/nomad-pledge-driver
• https://nomad-git-ce724-hashicorp.vercel.app/nomad/drivers/community/containerd > https://github.com/Roblox/nomad-driver-containerd
• https://nomad-git-ce724-hashicorp.vercel.app/nomad/drivers/community/nspawn > https://github.com/JanMa/nomad-driver-nspawn
• https://nomad-git-ce724-hashicorp.vercel.app/nomad/drivers/community/nomad-iis > https://nomad-iis.sevensolutions.cc/
• https://nomad-git-ce724-hashicorp.vercel.app/nomad/drivers/community/rookout > https://github.com/Rookout/rookout-nomad-driver
• https://nomad-git-ce724-hashicorp.vercel.app/nomad/drivers/community/firecracker-task-driver > https://github.com/cneira/firecracker-task-driver
• https://nomad-git-ce724-hashicorp.vercel.app/nomad/drivers/community/iis > https://github.com/Roblox/nomad-driver-iis
• https://nomad-git-ce724-hashicorp.vercel.app/nomad/drivers/community/jail-task-driver > https://github.com/cneira/jail-task-driver
• https://nomad-git-ce724-hashicorp.vercel.app/nomad/drivers/community/singularity > https://github.com/hpcng/nomad-driver-singularity

Links

Jira: CE-724
Deploy preview: https://nomad-git-ce724-hashicorp.vercel.app/nomad/plugins/drivers/community

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

• 13a59a5

[github-actions]

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