Upload source maps automatically in the SvelteKit SDK

[Lms24]

Add the Sentry Vite Plugin to upload source maps automatically for @sveltejs/adapter-node users:

### Research/PoC:
- [x] [Needs Research] find correct source maps generation config for SvelteKit apps + adapters
- [x] [**Spike**] Investigate why [server-side source maps are not emitted correctly](https://github.com/getsentry/sentry-javascript/discussions/5838#discussioncomment-4726617) ootb (upstream contribution?)
- [x] Ensure source map upload runs at the `buildEnd` hook
- [x] Avoid running upload twice
- [x] Try out DebugId (done, was erroneous, will revisit later)

### Tasks
- [x] #7787
- [ ] #7811
- [ ] https://github.com/getsentry/sentry-javascript/pull/7831
- [ ] https://github.com/getsentry/sentry-javascript/pull/7835
- [ ] #7846
- [ ] https://github.com/getsentry/sentry-javascript/pull/7863

ref #6692