feat: use -x option in backport script to improve tracability (#23984)

Add `-x` to backport script `git cherry-pick` command to include a
commit message reference to the original commit. This makes it easier to
trace where a cherry picked commit actually came from.

scripts/backport-pr.sh

@@ -96,7 +96,7 @@ git checkout -b "$backport_branch" "origin/${release_branch}"
 
 # Cherry-pick the merge commit.
 log "Cherry-picking ${merge_commit}..."
-if ! git cherry-pick "$merge_commit"; then
+if ! git cherry-pick -x "$merge_commit"; then
 	log ""
 	log "Cherry-pick failed due to conflicts."
 	log "Resolve the conflicts, then run:"