Add "debug merge queue" job (#13820)

#### Description

The condition in the "Merge freeze" CI workflow preventing the "Prepare
release" PR from blocking itself is no longer working after changes to
the OTel bot. This PR adds a temporary "Debug merge queue" job, which
prints the commit name, author name, and author email, to check the new
correct values for the bot.

#### Link to tracking issue
Updates #13789

#### Testing
Hard to test in advance, but the merge queue for this PR should give an
idea of whether the new job is working.

Author: jade-guiton-dd

.github/workflows/check-merge-freeze.yml

@@ -19,6 +19,18 @@ on:
 permissions: read-all
 
 jobs:
+  debug:
+    name: Debug merge queue
+    if: github.event_name == 'merge_group'
+    runs-on: ubuntu-latest
+    env:
+      MESSAGE: ${{ github.event.merge_group.head_commit.message }}
+      AUTHOR_NAME: ${{ github.event.merge_group.head_commit.author.name }}
+      AUTHOR_EMAIL: ${{ github.event.merge_group.head_commit.author.email }}
+    steps:
+      - run: |
+          echo "Merging commit '$MESSAGE' from '$AUTHOR_NAME' ('$AUTHOR_EMAIL')"
+
   check-merge-freeze:
     name: Check
     # This condition is to avoid blocking the PR causing the freeze in the first place.