Update DD_TRACE_PROPAGATION_STYLE default values

[rachelyangdog]

What does this PR do? What is the motivation?

Update DD_TRACE_PROPAGATION_STYLE default values to include baggage.

Merge instructions

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• Ready for merge

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Additional notes

[github-actions]

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Modified Files

• https://docs-staging.datadoghq.com/rachel.yang/add-baggage-default/tracing/trace_collection/trace_context_propagation/

[bm1549]

Aside from this page, there are a handful of other pages that should be updated as well

@duncanhewett how would you like us to handle those? Would you suggest we just update them for now, have them link to the main trace context propagation page, or something else?

[bm1549]

This will need to be rephrased a bit to include baggage

Suggested change

	**Note**: With multiple formats, extraction follows the specified order (for example, `datadog,tracecontext,baggage` checks Datadog headers first). The first valid context continues the trace; additional valid contexts become span links.
	**Note**: With multiple trace context formats, extraction follows the specified order (for example, `datadog,tracecontext` checks Datadog headers first). The first valid context continues the trace; additional valid contexts become span links. When `baggage` is included, it is added as [baggage](#baggage) to the existing context.

[buraizu]

Created DOCS-10563 for docs team review

[duncanhewett]

Aside from this page, there are a handful of other pages that should be updated as well

@duncanhewett how would you like us to handle those? Would you suggest we just update them for now, have them link to the main trace context propagation page, or something else?

I would just update them for now. I do think the configuration should remain documented on each SDK page but it would good to find a way to avoid the duplication of the content in the codebase to make maintenance easier.