Pre-Build Docker Images

[kgrubb]

Prerequisites

• [x] I have searched open and closed issues for duplicates.

Feature

We could possibly speed up a lot of our ci runs by pre-building the actions images, so that each pipeline doesn't have to build the docker image every time (they'd just fetch the existing image). Not sure what kind of performance gains we could get with this, but I think it'd probably be a significant enough speed boost to investigate!