Allow re-running of workflows

[ErikSchierboom]

• Don't open a new issue if it already exists
• Prevent pull request from being created more than once

[ErikSchierboom]

Note that I haven't yet tested the workflow, but I wanted to get feedback first

[ErikSchierboom]

I've not added this check to the steps that check for the repo being a tooling or track repo, as steps.is-tooling-repo.outputs.result == 'true' will be false anyway due to the step where that result is used. The same goes for the last steps that all check for steps.changes.outputs.changes == 'true', which will always be false due to the step to set that to true not being executed if the PR already exists

[SaschaMann]

Would be best to test this somewhere but it looks good to me. Limiting the listForRepo results with the right label and state should save us some API calls because we're probably not going to run into pagination.

[ErikSchierboom]

@SaschaMann
This is the issue creation being skipped: https://github.com/exercism/org-wide-files/runs/5464765618?check_suite_focus=true
This is the PR being created: https://github.com/exercism/org-wide-files/runs/5463961328?check_suite_focus=true
This is the PR being skipped: https://github.com/exercism/org-wide-files/runs/5464601595?check_suite_focus=true
This is a new run with a new repo as its argument: https://github.com/exercism/org-wide-files/runs/5464797097?check_suite_focus=true

[SaschaMann]

Those checks look good.

[SaschaMann]

Needs a rebase

[ErikSchierboom]

Rebased