Refactor Commons CSV maintainability hotspots

[DevNexus09]

Summary

This PR performs behavior-preserving refactors for maintainability hotspots identified in the code-smell report.

Changes include:

• Extracted private helpers in CSVFormat, CSVParser, Lexer, ExtendedBufferedReader, CSVPrinter, and CSVRecord.
• Reduced complex private method bodies without changing public behavior.
• Preserved public APIs, deprecated compatibility methods, predefined dialect constants, and existing semantics.
• Consolidated a small duplicated parser-test pattern using parameterized tests.

Validation

• mvn clean test
• mvn verify

Both passed with:

• 944 tests
• 0 failures
• 0 errors
• 11 skipped

Notes

These changes are focused only on maintainability/code-smell reduction and are intended to preserve existing Apache Commons CSV functionality.

[garydgregory]

Closing: Change for the sake of change. This kind of PR just eats up maintainers time for zero value compared to fixing bugs (see the recent changes for example fixes).