Turbopack: Server HMR infrastructure (#88870)
This adds some basic JavaScript/TypeScript infrastructure for Next to receive and handle server-side HMR updates from Turbopack.
This:
- Renames some existing hmr code as explicitly client hmr
- Adds counterpart apis for server hmr (e.g. subscribe to server HMR events via `project.serverHmrEvents()`)
- Add `__turbopack_server_hmr_apply__` runtime function (this is a stub for now, just logs on updates)
**Alternatives considered**
A single firehose for hmr events, pushing the filtering to the JS side. I figured separate dedicated apis would be cleaner since they’d have to be filtered and switched on anyway.
**In future PRs**
- Rust: Make Turbopack send 'partial' updates for server file changes
- Node dev runtime: Implement module factory replacement in `__turbopack_server_hmr_apply__`
- add client notification to trigger re-fetch of rsc
- e2e tests
