propagators/aws/xray: add test for Fields method

[Oloruntobi1]

Closes: #7054

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 75.8%. Comparing base (b0c0319) to head (83aa6e0).
Report is 1 commits behind head on main.

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #7073   +/-   ##
=====================================
  Coverage   75.8%   75.8%           
=====================================
  Files        207     207           
  Lines      19494   19494           
=====================================
+ Hits       14783   14785    +2     
+ Misses      4275    4273    -2     
  Partials     436     436           

see 1 file with indirect coverage changes

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.