In v8, we will use OpenTelemetry for performance instrumentation in Node packages - see #9842

### Tasks
- [ ] https://github.com/getsentry/sentry-javascript/issues/10898
- [ ] https://github.com/getsentry/sentry-javascript/issues/10900
- [ ] https://github.com/getsentry/sentry-javascript/issues/10902
- [ ] https://github.com/getsentry/sentry-javascript/pull/10960
- [ ] https://github.com/getsentry/sentry-javascript/pull/10997
- [ ] https://github.com/getsentry/sentry-javascript/pull/11033
- [ ] https://github.com/getsentry/sentry-javascript/pull/11239
- [ ] https://github.com/getsentry/sentry-javascript/pull/11016

This has a bunch of implications for the public API of Sentry:

• startTransaction() will be removed - instead, use the already existing startSpan, startSpanManual and startInactiveSpan APIs
  • Should we still provide startTransaction() and similar but make them noop/warn?
• The Sentry Transaction and Span type will be removed in favor of a singular new Span type
• In Node, OTEL Spans will be used. In Browser/Edge, we need to use a Span API that is compatible with OTEL Spans.
  • This means that e.g. span.setTag() and similar APIs will def. not work in Node
  • Should we make them work in non-OTEL environments?
  • Should we have the old APIs as noops or similar still?