Replace workflows' `set-output` with new way of defining variables in GH actions

[ggbecker]

Github workflows should use https://docs.github.com/en/actions/using-workflows/workflow-commands-for-github-actions#setting-an-output-parameter

instead of set-output directive. For example:

content/.github/workflows/automatus-cs8.yaml

Line 33 in 1e6e5eb

run: echo "::set-output name=FORK_POINT::$(git merge-base origin/$BASE_BRANCH ${{ github.event.pull_request.head.sha }})"

Reference: https://github.blog/changelog/2022-10-11-github-actions-deprecating-save-state-and-set-output-commands/

[marcusburghardt]

Fixed by #10588