[Spike] Document deploy process in all envs

[mehansen]

Description

The engineering team could benefit from a deeper understanding of what goes on when we deploy, especially for debugging build issues or ensuring that sufficient tests have been run. Examples of questions to be answered are:

• at what point in the process do certain tests get run? (e.g. on merge to main, build, deploy)
• when you run the GitHub action to deploy, how many containers are booting up and initializing the app and in what order?

Proposed solution

For each environment, document the following:

• what triggers the deploy
• steps, including tests
• when containers booted and when/how slot swap happens
• anything else?

For environments that have identical behavior, no need to duplicate info.