Update single comment for check compatibility

Instead of appending a new comment every time check compatibility runs,
this will instead update a single comment with the latest results. The
history of previous runs is retained in the comment as GitHub allows you
to view the edited revisions of any comment. This matches the behavior
of the codecov workflow and should substantially reduce noise in PRs.

Relates opensearch-project#9699

Signed-off-by: Andrew Ross <andrross@amazon.com>

.github/workflows/check-compatibility.yml

@@ -52,8 +52,18 @@ jobs:
         with:
           name: results.txt
 
+      - name: Find Comment
+        uses: peter-evans/find-comment@v2
+        id: fc
+        with:
+          issue-number: ${{ github.event.number }}
+          comment-author: 'github-actions[bot]'
+          body-includes: 'Compatibility status:'
+
       - name: Add comment on the PR
         uses: peter-evans/create-or-update-comment@v3
         with:
+          comment-id: ${{ steps.fc.outputs.comment-id }}
           issue-number: ${{ github.event.number }}
           body-path: results.txt
+          edit-mode: replace