Convert JSON Test Suite from blocking unit test to standalone reporting tool

[simbo1905]

Summary

Resolves #16 by converting the JSON Test Suite from a failing unit test that blocks builds into a comprehensive standalone reporting tool.

Key Changes

• Migrated JsonTestSuiteSummary from test to main using git mv, converted to executable tool with main() method
• Added Maven wrapper and exec plugin configuration for easy execution
• Disabled blocking unit test with @Disabled annotation - builds no longer fail
• Implemented robust encoding detection via RobustCharDecoder to handle malformed UTF-8, BOM detection, UTF-16/UTF-32, and permissive byte-to-char conversion
• Comprehensive API testing - now tests both Json.parse(String) and Json.parse(char[]) APIs
• Added security documentation warning about undocumented StackOverflowError vulnerabilities in upstream API

Test Results

• 318 files analyzed (0 skipped due to robust encoding)
• 99.3% overall conformance maintained
• 2 duplicate key failures are implementation choice, not bugs
• 26 files successfully processed via robust encoding detection

Usage

# Build and download test suite
./mvnw clean compile generate-test-resources -pl json-compatibility-suite

# Run human-readable report
./mvnw exec:java -pl json-compatibility-suite

# Run JSON output
./mvnw exec:java -pl json-compatibility-suite -Dexec.args="--json"

The tool now provides comprehensive JSON Test Suite analysis without blocking builds, exactly addressing the issue raised.