Add support in the Python SDK for the Baggage specificaition, as described in Sentry Developer Documentation.

Refer SDK Developer Documention for full details

Based originally on the propagation format for distributed context: Baggage

Should be applied in way that allows compatibility with other Sentry SDKs, ensuring proper distributed tracing functionality and simplifying intercommunications, ingestion, and being a good citizen with other 3rd party implementations working with baggage, via consumption or adding to.

PRs from the JS people on how they implemented baggage:

• Baggage Datenstrukturen/Operationen
• Baggage Daten in Envelope Header mitschicken
  • getsentry/sentry-javascript#5104
  • getsentry/sentry-javascript#5128
  • Mutability von Baggage wir erst in 5 behandelt
• Baggage an outgoing requests weitergeben (ohne Data population)
• [Release und Environment propagation](getsentry/sentry-javascript#5193
  Mutability von Baggage setzen:)
  • getsentry/sentry-javascript#5205
  • getsentry/sentry-javascript#5218