Speed up GitHub Action

[lorensr]

It would be nice if this workflow ran faster (with several PRs I've found myself waiting and checking back on the status and it's usually still in progress):

.github/workflows/ci.yml

Not high priority, and I don't have much experience/ideas around this—from a brief search: maybe more things in parallel, more caching, prebuilt docker images?

[bergundy]

I have some ideas on how to speed this up. I talked to the Temporal infra team about getting dedicated runners. Apart from that I have some other ideas. This is getting annoying to me too.

[mjameswh]

Covered in #1003

[mjameswh]

Completed in #1003