fix(spans): Set sentry.trace.status on segment spans

[mjq]

The product currently exposes sentry.trace.status to users (as trace.status). This is currently only set for v1 spans (extracted from the transaction's trace context's status field). Despite the name, it represents the transaction's status, not the whole trace.

For backwards compatibility we have to expose this on v2 spans as well. This only makes sense on segment spans (but segment enrichment will copy the value to all children). The order of precedence is:

1. Existing sentry.trace.status attribute (v1 span)
2. Existing sentry.status attribute (v1 span missing trace context status field)
3. Span's top-level status field (v2 and OTel spans)

I'm doing this in Relay because it:

• only involves individual spans (does not depend on a complete segment)
• is not related to the conversion of spans to EAP trace items

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🤖: Used Claude for the test cases

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[loewenheim]

Is this a temporary measure? Otherwise the sentry.trace.status attribute should be added to conventions.

[mjq]

@loewenheim

Is this a temporary measure? Otherwise the sentry.trace.status attribute should be added to conventions.

True, I'll add it (as well as sentry.status).

EDIT: getsentry/sentry-conventions#453