fix(logs): Structured Logs do not send ParentSpanId when no Span was active

[Flash0ver]

This is a follow-up PR
from #4462 (comment)
that is applying a change we made for the Serilog integration of Structured Logs
to the SDK-Logger and the Microsoft.Extensions.Logging integration,
when reading values for the attributes "trace_id" and "sentry.trace.parent_span_id".

Rather than using the TraceHeader,
instead use the currently active Span, or the Propagation Context as a fallback.

During testing I noticed, that there doesn't seem to be a behavioral difference in Sentry, hence the #skip-changelog.

---

Note

Structured Logs now derive trace_id from the active span or scope and only include sentry.trace.parent_span_id when an active span exists.

• Structured Logs behavior:
  • Read trace_id/parent_span_id via SentryLog.GetTraceIdAndSpanId(...) from the active Span; fall back to scope for trace_id only.
  • Omit sentry.trace.parent_span_id when no active span.
• Implementations updated:
  • Sentry.Extensions.Logging logger and DefaultSentryStructuredLogger now use the new helper (replacing GetTraceHeader).
  • Sentry.Serilog sink uses the helper; removes its local resolver.
  • Adds helper to SentryLog core type.
• Tests: Adjusted to validate new source of IDs and absence of parent_span_id without an active span.
• Changelog: Note about not sending Parent-Span-IDs without an active span.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 73.48%. Comparing base (e9f75ac) to head (50ee186).
⚠️ Report is 5 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4565   +/-   ##
=======================================
  Coverage   73.47%   73.48%           
=======================================
  Files         482      482           
  Lines       17679    17678    -1     
  Branches     3495     3493    -2     
=======================================
+ Hits        12989    12990    +1     
  Misses       3799     3799           
+ Partials      891      889    -2     

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[Flash0ver]

@sentry review

[alexsohn1126]

A couple of possibly dumb questions 😛

[alexsohn1126]

Looks good! Thanks for answering my questions 💯