Refactor concourse pipelines

[drewbo]

We'd like to refactor our concourse pipelines for greater consistency across our repos. We've set up pages-pipeline-tasks to assist with this. Roughly:

• Abstract common tasks into tasks/scripts
• Add common/repeated resources/resource types to the overlays here to be replaced by ytt
• Move all our repositories to having one long-running branch (main) and setup the pipelines so that PRs deploy to dev, merges to main deploy to staging, and new matching tags deploy to production
• Semi-automate the release process like in this repo: we have an auto-updating release branch which when merged creates a new tag/release/deploy to production
• Any other simplifications we see that can do across our pipelines now that container hardening is complete.

Resources:

• https://docs.google.com/spreadsheets/d/1WJqK-wKLrnxYZhd1RHq1w-t6RQu3a58JlU_UuW9NjcQ/edit#gid=0

Tasks

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1. Update CI pipeline pages-build-container#472
   +0
2. Use CI boot script pages-proxy#212
   +0
3. configure pipeline pages-mailer#43
   +0
4. Update CI Pipeline #4548
   +0
5. Update CI pipeline pages-redirects#249
   +0
6. Update CI Pipeline pages-cf-build-tasks#37
   +0

[drewbo]

Still likely to tinker with a few pipelines after the fact but this is done!