Add add-to-project step & rename workflow assign-issue workflow file

We are updating the workflows to auto-add new issues & PR to actions/cache project board.

.github/workflows/assign-issue.yml

@@ -1,16 +0,0 @@
-name: Assign issue
-on:
-  issues:
-    types: [opened]
-jobs:
-  run-action:
-    runs-on: ubuntu-latest
-    steps:
-    - name: Get current oncall
-      id: oncall
-      run: |
-        echo "CURRENT=$(curl --request GET 'https://api.pagerduty.com/oncalls?include[]=users&schedule_ids[]=P5VG2BX&earliest=true' --header 'Authorization: Token token=${{ secrets.PAGERDUTY_TOKEN }}' --header 'Accept: application/vnd.pagerduty+json;version=2' --header 'Content-Type: application/json' | jq -r '.oncalls[].user.name')" >> $GITHUB_OUTPUT
-    
-    - name: add_assignees
-      run: |
-        curl -X POST -H "Accept: application/vnd.github+json" -H "Authorization: Bearer ${{ secrets.GITHUB_TOKEN}}" https://api.github.com/repos/${{github.repository}}/issues/${{ github.event.issue.number}}/assignees -d '{"assignees":["${{steps.oncall.outputs.CURRENT}}"]}'