Pipeline cleanup from Jammy -> Noble update pains

Collecting noticed issues / deficiencies in the BOSH Director pipeline while fixing Noble related failures.

BRATs changes

• BRATs tests should load bosh-dns-release based on bosh-deployment/runtime-configs/dns.yml
• BRATs tests should upload brats/assets/linked-templates-release directly, see https://github.com/cloudfoundry/bosh/blob/main/ci/dockerfiles/docker-cpi/create-and-upload-release.sh
• BRATs specs should be CPI agnostic
• BRATs specs should optimize stemcell uploads (duplication)
• BRATs undo {canary,update}_watch_time: change: 120000-600000 => 60000-300000

BDRATs changes

• BDRATs specs should be CPI agnostic

Docker CPI changes

• docker-cpi-image creation should move to https://github.com/cloudfoundry/bosh-docker-cpi-release/
  • note duplication between start-bosh.sh (bosh repo) and test-integration.sh (docker-cpi repo)
  • Harmonize BOSH's start-bosh.sh with BOSH Docker CPI test-integration.sh
  • refactor ci/tasks/integration-test.sh to use start-bosh
• Docker CPI startContainerCommands should move into the container stemcell (aka "warden stemcell")
• Add tests that exercise Bosh DNS

Warden CPI changes

• warden-cpi-image creation should move to https://github.com/cloudfoundry/bosh-warden-cpi-release/

Upgrade Tests

• Upgrade tests should poll for director availability (rather than sleep)

BOSH Deployment

• Update bosh-deployment misc/dns-addon.yml to be noble compatible (no configure_systemd_resolved: true set)

Misc Pipeline Issues

• BBL envs leaking?
  • See #bosh-core-dev thread for context

Start by reading the referenced BRATs and BDRATs specs, ci/dockerfiles/docker-cpi/create-and-upload-release.sh, start-bosh.sh, test-integration.sh, integration-test.sh, and misc/dns-addon.yml. Run the relevant pipeline and upgrade tests, then track each listed cleanup item to completion across BOSH and the linked CPI repositories.