fix: check for key retriever in Parquet decryption properties conversion

[adamreeve]

Which issue does this PR close?

• Closes Improve conversion from FileDecryptionProperties to ConfigFileDecryptionProperties #21634.

Rationale for this change

Previously an error when retrieving the footer key was used as an indication that a key retriever was used, but this isn't reliable. A key retriever implementation might choose to return a footer key even if no key metadata is provided. This could mean that a footer key is set in the converted decryption properties but column keys are not correctly converted.

arrow-rs didn't previously expose whether a key retriever is used, but this was added in 59.0.0.

What changes are included in this PR?

Use the new FileDecryptionProperties::uses_key_retriever to determine whether FileDecryptionProperties uses a key retriever, rather than rely on getting an error when getting the footer key.

What is the testing strategy for this PR?

Updated existing unit test.

Are there any user-facing changes?

No, this changes an error message but should otherwise not affect users except if they had a key retriever implementation that would return footer keys without any metadata being provided.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 76.92308% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 81.72%. Comparing base (1b6dc92) to head (8208093).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
datafusion/common/src/config.rs	76.92%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #24866      +/-   ##
==========================================
- Coverage   81.72%   81.72%   -0.01%     
==========================================
  Files        1127     1127              
  Lines      416310   416312       +2     
  Branches   416310   416312       +2     
==========================================
- Hits       340224   340212      -12     
- Misses      56095    56108      +13     
- Partials    19991    19992       +1     

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[kosiew]

@adamreeve,

Thanks for working on this. The explicit uses_key_retriever() check looks like the right way to handle this. I just have one suggestion to make the regression test cover the original failure mode more directly.

[adamreeve]

Thanks for reviewing this @kosiew!

[kosiew]

🚀
@adamreeve
Thank you for your contribution.