chore: update mergify rules to push priority PRs to priority queue (#33334)

### Issue # (if applicable)

N/A

### Description of changes
Add a new mergify rule to push the priority PRs to priority queue.

### Checklist
- [X] My code adheres to the [CONTRIBUTING GUIDE](https://github.com/aws/aws-cdk/blob/main/CONTRIBUTING.md) and [DESIGN GUIDELINES](https://github.com/aws/aws-cdk/blob/main/docs/DESIGN_GUIDELINES.md)

----

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

Author: moelasmar

.mergify.yml

@@ -76,6 +76,27 @@ pull_request_rules:
     conditions:
       - base!=release
       - -title~=(WIP|wip)
+      - -label~=(blocked|do-not-merge|no-squash|two-approvers|priority-pr)
+      - -merged
+      - -closed
+      - author!=dependabot[bot]
+      - author!=dependabot-preview[bot]
+      - "#approved-reviews-by>=1"
+      - -approved-reviews-by~=author
+      # This is important! It makes the PR Linter work.
+      - "#changes-requested-reviews-by=0"
+      - status-success~=AWS CodeBuild us-east-1
+      - status-success=validate-pr
+  - name: automatic priority merge
+    actions:
+      comment:
+        message: Thank you for contributing! Your pull request will be updated from main and then merged automatically (do not update manually, and be sure to [allow changes to be pushed to your fork](https://help.github.com/en/github/collaborating-with-issues-and-pull-requests/allowing-changes-to-a-pull-request-branch-created-from-a-fork)).
+      queue:
+        name: priority-squash
+    conditions:
+      - base!=release
+      - -title~=(WIP|wip)
+      - label~=priority-pr
       - -label~=(blocked|do-not-merge|no-squash|two-approvers)
       - -merged
       - -closed