WIP: Apply paas scaffold to the saas scaffold.

[simesy]

This merges the paas scaffold into the original scaffold. To be ready for merge it also needs stuff to be ready outside of the PR:

• CAB approval
• Ansible task "update-scaffolding-files.yml" needs to safely detect and process existing saas projects into the new structure (or skip updating temporarily)
• Scaffold tooling "vet" tests should prevent saas users from changing key aspects of the repo.
• The not new problem of windows performance mounting /app

Internal tracking: GOVCMS-4225

[simesy]

Thought dump.

PaaS users on windows struggle with local development. Aside from the initial tooling setup, there can be really hard issues to solve if virus/malware scanning is enabled. Windows will be scanning the entire codebase while docker is trying to sync changes. Very obvious in composer install/update, but also docker pull looks like it's hanging while the image is being scanned for malware.

Ironically for SaaS, some of these slowness issues are mitigated, since we only mount ../themes and ../files. Not a new problem for SaaS, but an important one to be aware of in general as the platform grows. The distro is BIG, drupal is BIG, gulp/scss/npm theme setups can be HUGE (insert npm joke here).

Once Lagoon has internal registry support with Harbor, and we are deploying production images that are being built from a GitLab job, there is a baseline to revisit "lite development" for windows, like a docker-compose specifically for theme developers. But there have also been discussions about allowing SaaS users to run gulp/etc in Gitlab jobs, and this starts to make the gitlab IDE more compelling for lite theme development - I have witnessed many situations where this would be amazing.

Speaking of gulp jobs, the split gitlab CI which PaaS now has is ripe for adding a user-configurable gulp build job for SaaS users. If this PR ultimately gets merged I intend to follow up with that!