content-aware-hash experiment update (#164803)

- output to annotations which can be used from a simple url
- output summary to see if that's at all valuable

.github/workflows/content-aware-hash.yml

@@ -7,7 +7,7 @@ name: Generate a content aware hash for the Flutter Engine
 on: workflow_dispatch
 
 jobs:
-  hash:
+  generate-engine-content-hash:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout code
@@ -19,4 +19,8 @@ jobs:
 
       - name: Generate Hash
         run: |
-          git ls-tree HEAD DEPS bin/internal/release-candidate-branch.version engine | git hash-object --stdin
+          engine_content_hash=$(git ls-tree HEAD DEPS bin/internal/release-candidate-branch.version engine | git hash-object --stdin)
+          # test notice annotation for retrival from api
+          echo "::notice ::{\"engine_content_hash\": \"${engine_content_hash}\"}"
+          # test summary writing
+          echo "{\"engine_content_hash\": \"${engine_content_hash}\"" >> $GITHUB_STEP_SUMMARY