trace: detect rage restarts and deleted .next dirs (#92489)
**This is only sent if there is an explicit, user-provided
`--experimental-upload-trace` set.**
Adds two new attributes to the `start-dev-server` span when
`--experimental-upload-trace` is set:
- `rage-restart` — true if the server was restarted within 2 minutes of
last stopping
- `missing-next-dir` — true if the `.next` dir from the previous session
was deleted before restart
State (stop time + dist dir path) is written to a temp file outside
`.next` on graceful shutdown, so it survives `rm -rf .next`. Detection
results are passed to the child via `NEXT_PRIVATE_DEV_SPAN_ATTRS`,
following the same pattern as `NEXT_PRIVATE_ENABLED_FEATURES`.
Test Plan: Added an e2e test.
<!-- NEXT_JS_LLM_PR -->
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Co-authored-by: Will Binns-Smith <wbinnssmith@users.noreply.github.com>
Co-authored-by: Claude <noreply@anthropic.com>
