Add caching for GenericVersion instances in GenericVersionScheme

[gnodet]

Summary

This PR implements caching for GenericVersion instances in GenericVersionScheme to improve performance when parsing identical version strings repeatedly, which is common in dependency resolution scenarios.

Changes Made

Core Implementation

• Added ConcurrentMap<String, GenericVersion> cache in GenericVersionScheme with initial capacity of 256
• Modified parseVersion() method to use computeIfAbsent() for thread-safe caching
• Updated main method to use scheme.parseVersion() for consistency with caching approach

Test Improvements

• Added comprehensive caching tests in GenericVersionSchemeTest to verify same instances are returned for identical strings
• Created performance test class GenericVersionSchemeCachingPerformanceTest with tests for:
  • Performance comparison between cached and direct instantiation
  • Correctness verification
  • Concurrent access safety
• Updated test utilities to use shared scheme instances:
  • GenericVersionRangeTest.newVersion() now uses versionScheme.parseVersion()
  • UnionVersionRangeTest uses shared scheme instance instead of creating new ones

Benefits

1. Performance: Significant speedup for repeated parsing of identical version strings
2. Memory efficiency: Identical version strings share the same GenericVersion instance
3. Thread safety: Uses ConcurrentMap.computeIfAbsent() for safe concurrent access
4. Backward compatibility: No breaking changes to public API
5. Immutability: Safe to cache since GenericVersion is immutable

Technical Details

• Thread Safety: Uses ConcurrentHashMap with computeIfAbsent() for thread-safe lazy initialization
• Cache Key Strategy: Uses exact string representation as key ("1.0" and "1.0.0" are different entries)
• Memory Management: Initial capacity of 256 provides good performance for typical usage patterns

Testing

The implementation includes:

• Unit tests verifying caching behavior
• Performance tests demonstrating benefits
• Concurrent access tests ensuring thread safety
• Existing tests continue to pass, ensuring no regressions

This optimization is particularly beneficial in dependency resolution scenarios where the same version strings are parsed multiple times during graph traversal and conflict resolution.

Files Changed

• GenericVersionScheme.java - Core caching implementation
• GenericVersionSchemeTest.java - Added caching tests
• GenericVersionRangeTest.java - Updated to use scheme consistently
• UnionVersionRangeTest.java - Updated to use shared scheme instance
• GenericVersionSchemeCachingPerformanceTest.java - New performance test class

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Pull Request opened by Augment Code with guidance from the PR author

[cstamas]

Not for merge as is, as this cache just grows and never lets version instances free. We need to see some numbers first...
Ideal would be to keep cache in session or somehow tied to session? Flush per session? etc