[Console] Enable auto-merge in console_definitons (#270941)

## Summary
I noticed that we often approve the auto-generated PR, but we sometimes
forget to enable merge/auto-merge, so the PR sits there and never
merges. When that happens, the next weeks’ PRs don’t get generated, and
the whole weekly chain stalls. Enabling auto-merge at PR creation time
prevents this from being blocked by a missed manual step.
This change updates
`.buildkite/scripts/steps/console_definitions_sync.sh` so that after
creating the Console definitions sync PR it:

* Automatically enables auto-merge (squash) for that PR via gh pr merge
--auto --squash.
* Logs a warning if enabling auto-merge fails, without failing the step.

Author: SoniaSanzV

.buildkite/scripts/steps/console_definitions_sync.sh

@@ -66,15 +66,20 @@ main () {
   git push origin "$BRANCH_NAME"
 
   # Create PR
-  gh pr create \
+  pr_url=$(gh pr create \
     --title "$PR_TITLE" \
     --body "$PR_BODY" \
     --base "$BUILDKITE_BRANCH" \
     --head "$BRANCH_NAME" \
     --label 'backport:skip' \
     --label 'release_note:skip' \
     --label 'Feature:Console' \
-    --label 'Team:Kibana Management'
+    --label 'Team:Kibana Management')
+
+  report_main_step "Enabling auto-merge (squash)"
+  if ! gh pr merge "$pr_url" --auto --squash; then
+    echo "Warning: Failed to enable auto-merge (squash) for $pr_url"
+  fi
 }
 
 main