Get rid of all bash helpers (local dev)

[jechols]

The bash helpers for local dev and testing have gotten to be a mess, and bash is just too finicky to begin with. I just spent way too much time trying to figure out why migrations weren't happening properly, only to realize a make bin/migrate-database command was failing. If one runs the local dev scripts without paying close attention, it's not easy to tell that make runs can fail without stopped the "script". We can't do the usual set -eu stuff in here because these scripts are sourced into the local environment, so we have to handle errors more carefully. Which, in bash, is a huge pain.

So maybe it's time to build something in Go that gives us all the same commands / helpers, but without the bash.