validate pipeline fields together

[imjasonh]

I spent an embarrassing amount of time trying to debug why this failed:

- runs: autoconf/make
  with:
    opts: operator

When I figured it out, I wanted an error to stop me from making that mistake again.

This is incomplete, there are other combinations of pipeline fields that should be an error, but this is a start at least.

[imjasonh]

It looks like tini.yaml does this in Wolfi: https://github.com/wolfi-dev/os/blob/main/tini.yaml

I'm not sure if this is a bug, and that opts: are just ignored in this case. If that's so, it's even clearer this should be an error so folks don't point this footgun at themselves.