Fixes to drainpipe-dev deployments

[davereid]

Fixes #459
Fixes #460
Fixes #472

• Updates the Drainpipe-Dev workflow to no longer need DDEV and just works with raw Git.
• Uses the https://github.com/webfactory/ssh-agent action to add the drainpipe-dev deploy key using the DRAINPIPE_DEV_DEPLOY_KEY secret set in this repository.
• Adds a new workflow within drainpipe-dev itself to automate creating the releases when a tag is pushed.
• Adds the https://github.com/marketplace/actions/repo-lockdown workflow in drainpipe-dev to auto-close any issues or PRs filed.

Remaining Tasks

• Remove this branch from the push event listing

Follow-ups

• Could we utilize signed commits with https://github.com/planetscale/ghcommit-action? (maybe leave this as a low-priority follow-up)

[justafish]

🎉