feat(nextjs): Attach headers using client hook

[chargome]

Replaces the way we attach headers to root spans so this also works for both turbopack and webpack.

The data flow is now as follows:

1. Request comes in
2. http integration attaches the full normalized request on sdkProcessingMetadata on the scope
3. Nextjs creates the span
4. node client hook attaches the headers on the root span if sendDefaultPii is set

All of this still does not work for edge atm

closes #17568
closes #17802
closes #17803

[github-actions]

node-overhead report 🧳

Note: This is a synthetic benchmark with a minimal express app and does not necessarily reflect the real-world performance impact in an application.

Scenario	Requests/s	% of Baseline	Prev. Requests/s	Change %
GET Baseline	8,752	-	9,636	-9%
GET With Sentry	1,342	15%	1,444	-7%
GET With Sentry (error only)	6,207	71%	6,177	+0%
POST Baseline	1,200	-	1,179	+2%
POST With Sentry	520	43%	496	+5%
POST With Sentry (error only)	1,065	89%	1,022	+4%
MYSQL Baseline	3,331	-	3,310	+1%
MYSQL With Sentry	421	13%	375	+12%
MYSQL With Sentry (error only)	2,712	81%	2,658	+2%

View base workflow run