[epic] enable continuous deployment for hosted deployments

[mollykarcher]

What problem does your feature solve?

• Removes manual steps from the deployment process
• Ensures that deployments aren't left in a "partially" done state, as happened once recently
• Deployments happen faster

What would you like to see?

The RPC deployment process after new github releases are created is moved to a fully CD process.

• Creation of a new github release automatically deploys to the dev namespace
• Some validation is performed on dev. That could be:
  • We run the system-tests (we'd probably need to consider beefing those tests up, if so)
  • We practice OOD for some period of time and metrics alert if there are issues (we'd probably need to mirror traffic to get this assurance)
• Successful validation on dev automatically kicks off deploy to prd namespace
• Alerts (on success or failure) are sent back to some channel in slack that we can monitor

What alternatives are there?

Continue doing everything manually