Add `rose macro -V` command to `rtw-tests.yml` Github Workflow

[chrisbillowsMO]

The rose macro -V command should be added to the Github Workflow.

The command runs the all configuration validator macros as described in the Rose documentation here.

We added this as a step to the working practices for CMEW after an error arose in the Rose GUI that was not picked up by the other Rose validation steps.

[chrisbillowsMO]

Before I could add rose macro -V to the GitHub Action, running the command was revealing this error:

[V] metomi.rose.macros.DefaultValidators: issues: 3
    template variables=SITE=""
        Value "" should be "metoffice, jasmin"
    (opts=jasmin)template variables=SITE="jasmin"
        Value "jasmin" should be "metoffice, jasmin"
    (opts=metoffice)template variables=SITE="metoffice"
        Value "metoffice" should be "metoffice, jasmin"
[INFO] rose-suite.info

Observable in the Rose GUI here (as with CMEW):

This was solved in CMEW by removing the site options and making type=quoted. I've done this for RTW in the rose-meta.conf.

description=The site at which the Rose suite will run.
help=This value must be set in a site-specific configuration file located in
    =the 'opt/' directory.
- values="metoffice, jasmin"
+ type=quoted