Add the Registry to docker-compose.

- Add registry_migrations and registry definitions
- Add configuration & certs for registry
- Add initdb scripting for postgres to create dedicated db 'registry'
- Add configuration to webservice's config.yml.erb

Usage:

Adding the following as `/etc/docker/daemon.json` will allow insecure
access to the any registry that resolves to `127.0.0.1`.

```json
{
  "insecure-registries" : [ "127.0.0.1" ]
}
```

Related to https://gitlab.com/gitlab-org/charts/gitlab/-/issues/2423

Move to Debian Buster vs Debian Stretch.

Impacted by https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=962535

Impacting customers in the move from VMs (Ubuntu) to Debian Stretch in
containers of CNG.

Make further changes to ensure that we're not stating unicorn, where we
should be saying webservice, but also change from refernces to `Rails`
for documentation / description purposes.

- Expand list to include major application components Workhorse and
task-runner.
- Update verbiage on base images to point to Debian stretch-slim.
Alpine is used for small tasks, not a general base.

Use a print command for find that is compat with busybox

Fix sed command syntax for replacing the app subscription

Add a wait for dependencies script that can be used in init containers

Fix the db-migrate script syntax

Fxi db-migrate rake path, and bad if condition

Change our builds to use the current branch build cache

But still fall back to latest

Fix db-migrate status check

Use proper bash test syntax

Improve status test

Grab the hash from md5sum

Try to fix the volume permissions for upgrade status dir

Fix missing trailing command

Do a better job of catching success status

See if we can have the migrations wait for the dependencies to be up

Run bundle from correct directory

Add more output to the migration commands

Update sidekiq to be compatible with the wait-for command

Make sure the sidekiq wrapper is executable

Switch docker-compose file back to using latest

Describing the intended support for configurating the containers