chore: Sync Workflow Use main-passing-tests (#804)

## Summary

Use main-passing-tests to update platform instead of main. 
Slack notification if merge to main-passing-tests fails. 
Use deploy key for merging to main-passing-tests so we can lock down
pushes to it.

## Checklist
- [ ] Added Unit Tests
- [ ] Covered by existing CI
- [ ] Integration tested
- [ ] Documentation update



<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

- **Chores**
- Updated workflow authentication for improved security during branch
checkouts.
- Adjusted workflow triggers and dependencies to ensure jobs run in the
correct order and respond to the appropriate branch events.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Author: chewy-zlai

.github/workflows/push_to_canary.yaml

@@ -497,6 +497,7 @@ jobs:
         with:
           ref: main
           fetch-depth: 0
+          ssh-key: ${{ secrets.CHRONON_REPO_DEPLOY_KEY }}
       - name: Update Stable Branch
         env:
           TARGET_BRANCH: main-passing-tests
@@ -524,7 +525,7 @@ jobs:
 
 
   on_fail_notify_slack:
-    needs: [run_aws_integration_tests, run_gcp_integration_tests]
+    needs: [run_aws_integration_tests, run_gcp_integration_tests, merge_to_main-passing-tests]
     if: failure()
     runs-on: ubuntu-latest
 

.github/workflows/push_to_platform.yaml

@@ -1,9 +1,8 @@
 name: Push to Platform
 
 on:
-  pull_request:
-    types: [closed]
-    branches: [main]
+  push:
+    branches: [main-passing-tests]
 
 jobs:
   subtree-pull:
@@ -51,7 +50,7 @@ jobs:
           git remote add chronon [email protected]:zipline-ai/chronon.git || true
           
           git fetch chronon main
-          git subtree pull --prefix=chronon chronon main
+          git subtree pull --prefix=chronon chronon main-passing-tests
 
       - name: Push changes to platform
         run: git push origin main