Add Sveltekit server-side performance monitoring instrumentation

[AbhiPrasad]

Based on the POC from the SvelteKit discussion.

### Tasks
- [ ] https://github.com/getsentry/sentry-javascript/pull/7532
- [ ] https://github.com/getsentry/sentry-javascript/pull/7537
- [ ] https://github.com/getsentry/sentry-javascript/pull/7536
- [ ] https://github.com/getsentry/sentry-javascript/pull/7574
- [ ] https://github.com/getsentry/sentry-javascript/pull/7582
- [ ] #7598 
- [ ] #7652 

Depending on sveltejs/kit#9542 (and sveltejs/kit#9543) we might be able to significantly simplify the load instrumentation for users.