handle workflow runs that do not have a conclusion in [githubactionsworkflowstatus]

[chris48s]

Closes #8716

It was always too much to ask for this to go completely to plan 😆

When a build is not completed yet, it has a null value for .conclusion e.g:

status: 'in_progress',
conclusion: null,

This PR allows .conclusion to be null and requires a non-null value for status which we can fall back to.

[chris48s]

Values for status are taken from

https://docs.github.com/en/rest/actions/workflow-runs?apiVersion=2022-11-28#get-a-workflow-run

I was in two minds about whether to add all the status values to build-status.js and attempt to classify them. The solution I've settled on is to leave that as-is and if we fall back to a status value and we don't have a formatting rule for it, just use default lightgrey for formatting.

I was also in two minds about whether to use a closed list here or allow any string (but make it required). Open to feedback on it..

[shields-ci]

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[calebcartwright]

Schema proposal works for me 👍 In general I'd have been more inclined to grab a transform function and unit test, but no objections to this since you've already battled and defeated the nock intercepts 😄

[calebcartwright]

Going to go ahead and let the bots merge this and then will run a deploy later tonight