Add Buildkite to preview links GitHub action

[joepeeples]

Description

Per elastic/docs#2837 (comment), our PRs will start using Buildkite to generate previews but we'll need to revise our GitHub action (docs-preview-links.yml) to provide the URLs to those previews.

ℹ️ TIP: Follow elastic/docs#2843, which looks to provide a common GitHub action template that all docs teams can use...

### Tasks
- [x] Add the new shared action — https://github.com/elastic/security-docs/pull/4390
- [x] Test it — https://github.com/elastic/security-docs/pull/4395
- [x] Remove the old action — https://github.com/elastic/security-docs/pull/4406
- [x] Test it again? — https://github.com/elastic/security-docs/pull/4411
- [x] Backport the changes so we can get previews in previous branches

### Backport PRs
- [ ] https://github.com/elastic/security-docs/pull/4421
- [ ] https://github.com/elastic/security-docs/pull/4430
- [ ] https://github.com/elastic/security-docs/pull/4429
- [ ] https://github.com/elastic/security-docs/pull/4428
- [ ] https://github.com/elastic/security-docs/pull/4427
- [ ] https://github.com/elastic/security-docs/pull/4426
- [ ] https://github.com/elastic/security-docs/pull/4425
- [ ] https://github.com/elastic/security-docs/pull/4424
- [ ] https://github.com/elastic/security-docs/pull/4423
- [ ] https://github.com/elastic/security-docs/pull/4422
- [ ] https://github.com/elastic/security-docs/pull/4420
- [ ] https://github.com/elastic/security-docs/pull/4419
- [ ] https://github.com/elastic/security-docs/pull/4418

[nkammah]

@joepeeples you can indeed use the generic action by defining a workflow like this once elastic/docs#2843 is merged.

Comm is on its way.

[joepeeples]

Backporting to all of 8.x to help with anticipated image cleanup efforts. Also backporting 7.17 to catch the most recent 7.x branch.