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 90.90909% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 81.61%. Comparing base (fefc227) to head (71a2832).

Files with missing lines	Patch %	Lines
datafusion/common/src/config.rs	90.90%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #24866      +/-   ##
==========================================
- Coverage   81.61%   81.61%   -0.01%     
==========================================
  Files        1123     1123              
  Lines      409392   409398       +6     
  Branches   409392   409398       +6     
==========================================
- Hits       334143   334124      -19     
- Misses      55630    55652      +22     
- Partials    19619    19622       +3     

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