New Find Dockerfile in PR and Build

[erinyoung]

These github action yml files are intended to replace test-PR-dockerfiles.yml.

• find_new_pr_dockerfile.yml uses tj-actions/changed-files to identify if a PR contains a new Dockerfile. It then creates a json of all the Dockerfiles in the PR and will pass them to
  • build_and_test_pr_dockerfile.yml : builds a dockerfile to 'builder' (optionally), 'app', and 'test' stages. Will then check the 'app' stage for labels, the workdir, a non-root user, check for some common nextflow depdencencies, run trivy, and generate a report back to the PR for each dockerfile.
  • lint_pr_dockerfile.yml : does not build anything, instead looks at the file for linting with hadolint, and some common layers (e.g. CMD)

Most of the text on test-PR-dockerfiles.yml is for testing purposes, and can probably be removed if we're confident they work.

[erinyoung]

Closes #1615

[erinyoung]

Closes #1249

[kapsakcj]

Plan:

• merge the PR and then test the new deploy workflow on an image that needs to be deployed
  • If new deploy workflow fails, then we can still use the old “manual-deploy” workflow