[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 (ec7a0d8, 189367d, fc15a27, c922146)
• ✅ login: Kielek / name: Piotr Kiełkowicz (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.