Handle GitHub runners possibly running out of space

[edmundmiller]

          sorry this feels very draft status. move it into a another PR before merging this one

Originally posted by @mashehu in #6286 (comment)

  # get-number-of-shards:
  #   runs-on: ubuntu-latest
  #   outputs:
  #     # Needs to be a json array
  #     shards: ${{ steps.shards.outputs.shards }}
  #     total_shards: ${{ steps.shards.outputs.total_shards }}
  #   steps:
  #     - name: Install nf-test
  #       uses: nf-core/setup-nf-test@v1
  #       with:
  #         version: ${{ env.NFT_VER }}

  #     - id: shards
  #       run: |
  #         nftest_output=$(nf-test test --dry-run --changed-since HEAD^ --filter process --follow-dependencies)
  #         number_of_shards=$(echo $nftest_output | grep -o 'Found [0-9]* related test' | tail -1 | awk '{print $2}')
  #         three_tests_per_shard=$(echo $(($number_of_shards / 3)) | awk '{print int($1+0.5)}')
  #         shards_array=$(for shard in $(seq 1 $number_of_shards); do echo $shard; done | tr ' ' '\n' | jq -R . | jq -s .)
  #         echo "shards=${shards_array}" >> $GITHUB_OUTPUT
  #         echo "total_shards=${number_of_shards}" >> $GITHUB_OUTPUT

WIP Code

[edmundmiller]

Tested in #6716 with some examples. We'll see how many issues we run into with it.