Migrate R4AvroConverterCustomProfileTest to JUnit 5 with cross-platform support

[Shiva-code-code]

This pull request updates R4AvroConverterCustomProfileTest to use JUnit 5 (jupiter) instead of JUnit 4, while still keeping the original JUnit 4 dependency for backward compatibility with existing tests.

Key changes:

Switched from @BeforeClass and Assert.* to JUnit 5 equivalents (@BeforeAll, Assertions.*).

Updated the resource path handling to use URI and Paths.get() to ensure compatibility across both Windows and Unix-based systems.

No business logic or assertion logic was changed—just a migration of syntax and setup.

Tested locally on Windows with mvn test, and everything runs as expected.
Open to feedback or changes if anything needs to be adjusted.xxx

[google-cla]

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[chandrashekar-s]

@Shiva-code-code if this change is ready for review, then can you please assign the reviewer, either @bashir2 or myself? Also, since this is your first contribution to the repo, can you please look at the comment made by the @google-cla bot in this PR.

[Shiva-code-code]

Hi @chandrashekar-s, thanks for the follow-up. I’ve signed the CLA and the PR is now ready for review. Since I don’t have permission to assign reviewers, tagging you here as requested. Let me know if anything needs adjustment!

[chandrashekar-s]

Thanks @Shiva-code-code for the update, I will have a look and share my feedback soon.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 46.80%. Comparing base (0cd9c1f) to head (16f6400).

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #1362      +/-   ##
============================================
- Coverage     50.28%   46.80%   -3.49%     
+ Complexity      698      666      -32     
============================================
  Files            90       90              
  Lines          5803     5803              
  Branches        798      798              
============================================
- Hits           2918     2716     -202     
- Misses         2587     2800     +213     
+ Partials        298      287      -11     

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