feat: Add is_remote flag in exporter for spans and span links

[nikhilmantri0902]

Fixes #3152
Design discussion issue (if applicable) #

Changes

Update OTLP exporter to fill the relevant bits in SpanFlags.

Merge requirement checklist

• CONTRIBUTING guidelines followed
• Unit tests added/updated (if applicable)
• Appropriate CHANGELOG.md files updated for non-trivial, user-facing changes
• Changes in public API reviewed (if applicable)

[codecov]

Codecov Report

❌ Patch coverage is 92.78351% with 7 lines in your changes missing coverage. Please review.
✅ Project coverage is 80.7%. Comparing base (6f75c58) to head (54a69b4).
⚠️ Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
opentelemetry-proto/src/transform/trace.rs	91.9%	7 Missing ⚠️

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #3153   +/-   ##
=====================================
  Coverage   80.6%   80.7%           
=====================================
  Files        126     126           
  Lines      22195   22286   +91     
=====================================
+ Hits       17898   17986   +88     
- Misses      4297    4300    +3     

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[Copilot]

Pull Request Overview

Implements span flags support for the isRemote property in the OTLP exporter as specified in issue #3152. This change enables proper setting of OTLP span flags based on whether the parent span context is remote or local.

• Added parent_span_context field to SpanData structures to store parent span context information
• Implemented build_span_flags function to set appropriate flags (0x100 for local, 0x300 for remote spans)
• Updated all span creation sites to include the new field and comprehensive test coverage

Reviewed Changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
opentelemetry-sdk/src/trace/export.rs	Added parent_span_context field to public SpanData struct
opentelemetry-sdk/src/trace/span.rs	Added field to internal SpanData and updated export data building
opentelemetry-sdk/src/trace/tracer.rs	Populated parent_span_context field during span creation
opentelemetry-proto/src/transform/trace.rs	Implemented build_span_flags function and updated span/link transformations
opentelemetry-zipkin/src/exporter/model/span.rs	Updated test data with new field
opentelemetry-sdk/src/trace/span_processor.rs	Updated test span data creation
opentelemetry-sdk/src/testing/trace/span_exporters.rs	Updated test helper function
opentelemetry-sdk/benches/batch_span_processor.rs	Updated benchmark span data
opentelemetry-otlp/src/exporter/http/mod.rs	Updated test span data
opentelemetry-sdk/CHANGELOG.md	Documented the new feature
opentelemetry-proto/CHANGELOG.md	Documented the transformation changes

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