fix(job-runner): move job manifest path

[onewland]

We found that we cannot rely on configmaps that mount as a specific file in k8s: they don't update without a restart (https://kubernetes.io/docs/concepts/storage/volumes/#using-subpath)

But, we cannot overwrite the contents of snuba/manual_jobs/ by mounting configuration there because we rely on source code in that directory. So we are moving this config to a new directory that doesn't pollute anything else (snuba/env).

Next step:

• updating the mount in ops to point to snuba/env