[v8] New Performance APIs

[mydea]

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?

[danielkhan]

1. Avoid NPEs. This means that we should noop+warn as suggested.
2. The same applies to setTag(). Yet, doesn't OTel offer something similar? Can we alias that?

[mydea]

re 2.: We have to re-write them to attributes, which I guess we can do 🤔

But also, important to note, that we currently don't really show some of this data for spans anyhow. Tags at least are not shown I think, not sure what is shown 🤔

[danielkhan]

But also, important to note, that we currently don't really show some of this data for spans anyhow. Tags at least are not shown I think, not sure what is shown

They might still be used for filters in Dashboards, I guess?

[mydea]

We should def. make a list of things that are/are not shown for transactions and spans right now, so we can make sure the user experience remains stable!