Exclude blocking spans from trace work accounting (#99685)
## Summary
Stacked above #99254. Allow `blocking = true` on elapsed-duration events
and entered tracing spans, using the same ignore-self-time accounting as
existing `blocking` spans.
Waiting durations otherwise inflate concurrency and CPU totals even
after the tasks yield—for example, a pending fetch emits overlapping
request and attempt durations. Blocking spans now keep their elapsed
ranges and metadata, but contribute no own CPU time, corrected time or
concurrency, and do not affect other work's correction factor. Counted
descendants remain included.
Classify network and Node.js pool-acquisition waits as blocking, while
keeping Node.js startup, initialization and evaluation counted as
external work. Missing/false attributes preserve legacy accounting. No
trace format or viewer payload changes.
Existing name-exempt `thread`/`blocking` spans also retain their full
elapsed end now, rather than dropping it along with self-time.
Attributes are classified at creation, not retroactively via record
updates. External-work durations remain elapsed approximations, not
OS-measured CPU time.
## Verification
- 85 trace-server/trace-utils tests passed, including new reader
regressions for flags, retained ranges, counted children, correction
factors and live cache invalidation; affected Rust producers and native
bindings compile.
- Rebuilt trace server queried over WebSocket: the 40-wait fixture
changes from concurrency 80 to 0 during the wait when its duration
events carry `blocking = true`. Root CPU totals drop from 8002ms to the
2ms entered work; waiting leaf retains its 100ms elapsed range with zero
CPU/corrected duration.
- No new benchmark screenshot: actual raw-reader tests and the
rebuilt-server fixture verify the changed accounting.
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Co-authored-by: vercel-fleet-prod[bot] <318278635+vercel-fleet-prod[bot]@users.noreply.github.com>
Co-authored-by: Tobias Koppers <1365881+sokra@users.noreply.github.com>
