[all] prepare SDK 2.0 prerelease

[pichlermarc]

Description

We're doing a prerelease for SDK 2.0 (#5148) before going for an actual release to smooth over the transition and to give us some room to test the changes.

This issue is considered done when

• a pre-release has been published for SDK 2.0 (stable/experimental) and the packages are available via npmjs.org

[pichlermarc]

All necessary PRs are merged. Missing a workflow run when we're ready to actually do the pre-release (aiming for Feb 24).
I'll keep updating this issue on progress - missing items:

• Perf: avoid internal object format transformations during export #4385
  • PR pending
• Do not validate tracestate #790
  • Pending reviews on feat(core)!: defer tracestate validation until needed #5499

[pichlermarc]

Pre-release has been published, see announcement here. Final version is still pending some changes, more pre-releases to follow.