Edits to turbopackFileSystemCache (#96531)
- Rework the
`/docs/app/api-reference/config/next-config-js/turbopackFileSystemCache`
API reference.
- Adjust the table notes in
`/docs/app/api-reference/turbopack#configuration` — `[^1]` works well,
but the table notes are auto-magically placed at the bottom of the page.
Going with this hand rolled table notes for now.
- Tidy the Build Caching section in
`/docs/app/api-reference/turbopack#configuration`
- Update the Upgrade to version 16 section on dev/build cache
- Removed the `Build caching` from Webpack gaps
- Added Filesystem caching to Performance and Fast Refresh
