feat(nextjs): Support Next.js proxy files

[chargome]

closes #17894

E2E Tests TBD

[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	9,035	-	9,065	-0%
GET With Sentry	1,378	15%	1,339	+3%
GET With Sentry (error only)	6,170	68%	6,068	+2%
POST Baseline	1,196	-	1,170	+2%
POST With Sentry	550	46%	481	+14%
POST With Sentry (error only)	1,068	89%	1,029	+4%
MYSQL Baseline	3,339	-	3,244	+3%
MYSQL With Sentry	521	16%	471	+11%
MYSQL With Sentry (error only)	2,727	82%	2,657	+3%

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