Fix client component loading span timing (#96455)
## Summary
- Measure the existing client-component loading span from its first
observed start through the latest module or chunk settlement.
- Keep overlapping and nested loads within one valid timing interval
instead of accumulating durations onto the first start time.
- Preserve the original `loadChunk` promise identity while observing
both fulfilled and rejected settlements.
- Handle rejected chunk loads without creating a second unhandled
rejecting promise.
- Avoid ending the span while another tracked load remains pending.
This corrects an existing span; it does not introduce a new span type.
## Verification
- `pnpm exec jest --runInBand
packages/next/src/server/client-component-renderer-logger.test.ts`
- The final focused Request Insights matrix passed 10 suites and 82/82
tests, including overlapping, nested, pending, fulfilled, and rejected
client loads.
- `pnpm --filter=next build`
