feat(tanstackstart-react): Auto-instrument server function middleware

[nicohrubec]

Extending auto-instrumentation to non-global server function middleware.

TSS function middleware docs

Closes #18847

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

^{Bugbot Autofix is OFF. To automatically fix reported issues with Cloud Agents, enable Autofix in the Cursor dashboard.}

[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	8,552	-	9,277	-8%
GET With Sentry	1,544	18%	1,793	-14%
GET With Sentry (error only)	5,732	67%	6,303	-9%
POST Baseline	1,157	-	1,199	-4%
POST With Sentry	533	46%	613	-13%
POST With Sentry (error only)	1,017	88%	1,064	-4%
MYSQL Baseline	3,092	-	3,382	-9%
MYSQL With Sentry	406	13%	507	-20%
MYSQL With Sentry (error only)	2,533	82%	2,727	-7%

View base workflow run