Trace upload: include experimental flag states (#89845)
This includes the set of experimental flag states in events sent to the
trace upload receiver when `--experimental-trace-upload` is set. It only
includes a subset of experimental flags (so things like the trace upload
flag itself isn't meaninglessly sent).
Since reporting is often limited to the scope of a single span, the flag
state attributes are denormalized and copied onto every descendent span.
Limiting the set of flags prevents this from being unnecessarily large.
Test Plan: Added `test/development` test and built an app and verified
these tags are sent with `NEXT_TRACE_UPLOAD_DEBUG`
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Co-authored-by: vercel[bot] <35613825+vercel[bot]@users.noreply.github.com>
Co-authored-by: Luke Sandberg <lukesandberg@users.noreply.github.com>
