Refactor the JS script file loading code so that it's tied to the `fs.FS` interface for longer, and less to the specifics of our `embed.FS` instance. This should make it possible to use other filesystems, like a real on-disk one, to load scripts.
sleep_repeats
echo-sleep-test
assert.NoError()
assert.Nil()
job_compilers/path.go
js_path.go
job_compilers/process.go
js_process.go