[ty] Ecosystem analyzer: timing report (#20571)

## Summary

Generate a timing diff across the whole ecosystem and deploy it to
CloudFlare pages. The timing information is collected already, we just
need to create and upload the HTML report.

The timing results are just based on a single run. No statistical
analysis across multiple runs or similar is performed. This means that
results can be noisy, as can be seen on this PR, where we see slowdowns
up to 1.26× and speedups down to 0.89×, even though the change should be
neutral. Across all projects, these random events cancel out and we see
an average factor of 1.01×. So I think this feature can still be
interesting, given that it comes "for free". We just need to keep in
mind that it will be noisy, and shouldn't read too much into these
results.

## Test Plan

CI run on this PR (see the new *timing results* link).

.github/workflows/ty-ecosystem-analyzer.yaml

@@ -95,6 +95,14 @@ jobs:
             --new-name "$REF_NAME" \
             --output diff-statistics.md
 
+          ecosystem-analyzer \
+            generate-timing-diff \
+            diagnostics-old.json \
+            diagnostics-new.json \
+            --old-name "main (merge base)" \
+            --new-name "$REF_NAME" \
+            --output-html dist/timing.html
+
           echo '## `ecosystem-analyzer` results' > comment.md
           echo >> comment.md
           cat diff-statistics.md >> comment.md
@@ -118,7 +126,7 @@ jobs:
           DEPLOYMENT_URL: ${{ steps.deploy.outputs.pages-deployment-alias-url }}
         run: |
           echo >> comment.md
-          echo "**[Full report with detailed diff]($DEPLOYMENT_URL/diff)**" >> comment.md
+          echo "**[Full report with detailed diff]($DEPLOYMENT_URL/diff)** ([timing results]($DEPLOYMENT_URL/timing))" >> comment.md
 
       - name: Upload comment
         uses: actions/upload-artifact@ea165f8d65b6e75b540449e92b4886f43607fa02 # v4.6.2
@@ -137,3 +145,9 @@ jobs:
         with:
           name: diff.html
           path: dist/diff.html
+
+      - name: Upload timing diff
+        uses: actions/upload-artifact@ea165f8d65b6e75b540449e92b4886f43607fa02 # v4.6.2
+        with:
+          name: timing.html
+          path: dist/timing.html