app-run: add opts into the rose-app-run.conf

[oliver-sanders]

Note This applies to rose app-run and rose task run.

When a rose application is run, we output the flattened configuration to the rose-app-run.conf file.

Any optional configs or CLI options are applied before this file is written out, so this exists to reference the exact configuration run.

It might be useful to record any optional configurations that the app was run with in this file for ease of reference.

E.G:

!opts=foo bar baz

[command]
default=true

Note, I have made opts an "ignored" variable here as the opts have already been applied (so are no longer a functional part of the configuration) and because the opt/ files are not present at this point (so leaving it "enabled" would prevent you from being able to parse this config at a later date).

See https://cylc.discourse.group/t/rose-any-way-to-get-list-of-opt-conf-keys-used/990/3