[Instrumentation.AWS]: always add context propagation data to requests

[cfbao]

Fixes #2345

Changes

Move code that adds context propagation data to requests into a dedicated method AddPropagationDataToRequest, and always run that regardless of sampling decision.

Merge requirement checklist

• CONTRIBUTING guidelines followed (license requirements, nullable enabled, static analysis, etc.)
• Unit tests added/updated
• Appropriate CHANGELOG.md files updated for non-trivial changes
• Changes in public API reviewed (if applicable)

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: cfbao / name: Chenfeng Bao (c922146, ec7a0d8, 5c222f3, fc15a27, 189367d, 8b17b8a)
• ✅ login: Kielek / name: Piotr Kiełkowicz (430d9ed, 50cc6c3, 47aa775)

[cfbao]

There's no existing unit tests in this area, but I've verified that correctly adds relevant message attribute to SQS requests using the script showed in #2345.

[ppittle]

@cfbao - Thank you for the contribution!

There's no existing unit tests in this area, but I've verified that correctly adds relevant message attribute to SQS requests using the script showed in #2345.

Would it be possible to add some unit test coverage around this feature?

Otherwise, this looks good to me.

[cfbao]

@ppittle Oh I missed what these instrumentation tests were doing.
Added coverage on SQS message attributes for both sampled and not sampled requests now.

[cfbao]

Fixed markdownlint issue.

This test failure seems unrelated to this change though:
https://github.com/open-telemetry/opentelemetry-dotnet-contrib/actions/runs/12579606871/job/35060088493#step:7:72
or at least I'm not able to repro locally.

[Kielek]

Approving and merging based on @ppittle decision.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 0.00%. Comparing base (71655ce) to head (430d9ed).
Report is 678 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #2447       +/-   ##
==========================================
- Coverage   73.91%       0   -73.92%     
==========================================
  Files         267       0      -267     
  Lines        9615       0     -9615     
==========================================
- Hits         7107       0     -7107     
+ Misses       2508       0     -2508     

see 263 files with indirect coverage changes