Use MWC for search input

[justinfagnani]

This does the minimum I can see to get MWC components working in Lit SSR:

• Exclude them from server rendering with a custom renderer that wraps and conditionally disables LitElementRenderer
• Add a FallbackRenderer that doesn't render a shadow root
• Patch globalThis with dummy classes that MWC uses in decorator metadata

[github-actions[bot]]

A live preview of this PR will be available at the URL below and will update on each commit. = The build takes ~5-10 minutes, and will 404 until finished.

https://pr1422---site-khswqo4xea-wl.a.run.app/

Warning Until our Cloud Run project is public, only authorized users can view the above URL. The easiest way to view it authenticated is to run the following proxy command and visit http://localhost:5453

(gcloud beta run services proxy --project=webcomponents-org-test --region=us-west2 --tag=pr1422 --port=5453 site \
& gcloud beta run services proxy --project=webcomponents-org-test --region=us-west2 --tag=pr1422 --port=6453 catalog)