Review CI optimizations

[shaneutt]

Problem Statement

When we started with this project we put together some CI workflows which do-the-thing.yaml and served us fine for the early days, however we should review what we have soon to look for optimizations for CI efficiency and speed. Wait until https://github.com/Kong/blixt/milestone/2 is done before doing this as there will be a lot of new CI content at that point.

Prerequisites

• [ ] https://github.com/Kong/blixt/milestone/2

Checklist

• [ ] check that we're caching Go builds well for testing, linting, e.t.c. (perhaps particularly for golangci-lint jobs)
• [ ] look for opportunities to improve the speed of workflows to make PR checks and other CI jobs faster
• [ ] look for opportunities to improve the targeting of workflows to reduce waste (e.g. don't run docker builds for README updates, e.t.c.)