Hydration library for code components

Closes #3500058

This MR

• Adds an Astro project as an npm workspace
  • using npm workspace means this new library's package.lock and node_modules dependencies are part of /ui/package.lock and /ui/node_modules instead of having its own in its directory.
  • Astro built files are outputted in /ui/lib/astro-hydration/dist
• Added README.md
• astro-hydration's build step also calls a extract-hydration-script.js that writes the necessary hydration code from /astro-hydration/dist/index.html to a file.
• Updates the build step in /ui/package.json to also build this Astro project
• Removes old /astro-bundles directory that was added in the interim
• Replaces usages of path with /astro-bundles to this new library