feat: Update WAF install and configuration steps

[ADubhlaoich]

Proposed changes

This commit adds a necessary signature command to Alpine Linux, Debian &
Ubuntu installation steps. It further improves installation use cases by
adding some troubleshooting guidance to post-installation checks.

Similarly, policy and bundle-specific troubleshooting guidance has been
added to the compiler page. Finally, information on Bot signatures has
been added, with contextual links added or updated for logical
connections between use cases.

Checklist

Before sharing this pull request, I completed the following checklist:

• I read the Contributing guidelines
• My branch adheres to the Git conventions
• My content changes adhere to the F5 NGINX Documentation style guide
• If my changes involve potentially sensitive information¹, I have assessed the possible impact
• I have waited to ensure my changes pass tests, and addressed any discovered issues

Footnotes

1. Potentially sensitive information includes personally identify information (PII), authentication credentials, and live URLs. Refer to the style guide for guidance about placeholder content. ↩

[github-actions]

✅ Deploy Preview will be available once build job completes!

Name	Link
😎 Deploy Preview	https://frontdoor-test-docs.nginx.com/previews/docs/1296/

---

[travisamartin]

Can you comment in the AC for the PR that the updated installation steps were tested and verified? Any time an install guide is updated, we should verify the changes -- installation is a first impression.

[ADubhlaoich]

@travisamartin I have confirmation of the installation step changes working from a principal solutions engineer who tested it in a lab, though I am waiting for word back from an active customer case to double-confirm it.