ci: improve pr-remove-preview workflow

[f-hollow]

Description

Currently, the pr-remove-preview workflow fails, because it doesn't have access to the repo secrets. I didn't test this workflow properly before, because its priority was not high. Now I got around to it.

I split the workflow into two (the same way as pr-build-preview and pr-deploy-preview):

• The PR-side job triggered by the pull-request event
• The upstream repo side job triggered by the workflow_run event

On PR closure or merge, the preview is removed as well as all comments with links to PR preview.

Changed the prefix for all workflows triggered by workflow_run to prw-.

Related

• Is there an easy way to preview the new article? #43

Testing

All testing was done here.

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Checklist

Before submitting a Pull Request, please ensure the following:

• 🚨 This PR does not introduce breaking changes.
• All CI checks (GH Actions) pass.
• Documentation is updated as needed.
• Tests are updated or added as necessary.
• Code is well-commented, especially in complex areas.
• Git history is clean — commits are squashed to the minimum necessary.

[f-hollow]

I already tested it, so I will merge it.

Once merged, the final test will be to make sure that both the preview and the comments with PR preview link are removed.

Update:

The mentioned actions were successfully completed by the workflow!