Add `traceparent` header support for Browser SDKs

[mydea]

We want to implement the propagateTraceparent option for browser SDKs only: https://develop.sentry.dev/sdk/telemetry/traces/#propagatetraceparent

Server SDKs do not need to implement this. The goal is that users with a sentry-instrumented frontend can interop with pure OTEL-instrumented backends. If this setting is set, the traceparent header should be set in addition to existing headers - also see https://develop.sentry.dev/sdk/telemetry/traces/distributed-tracing/#w3c-trace-context-header

[linear]

JS-892 Add `traceparent` header support for Browser SDKs

[github-actions]

A PR closing this issue has just been released 🚀

This issue was referenced by PR #17509, which was included in the 10.10.0 release.