fix: otel error spans from streamed responses (#86955)
When an error is thrown inside a Suspense boundary during streaming SSR,
the error was not being captured in the "render route (app)" span. This
happened because `getTracer().wrap()` ends the span as soon as the
stream is created and returned, but errors inside Suspense boundaries
occur asynchronously during stream consumption.
This PR changes the span management from using `wrap()` to manually
calling `startSpan()` and tracking the span lifecycle. The span now
stays open until `allReady` resolves or rejects. A new `withSpan()`
helper was added to the tracer to properly activate the span context so
child spans are parented. Error handlers now accept an optional
`spanToRecordOn` parameter to record exceptions on the correct span
rather than relying solely on the active scope span.
Fixes #86517
