Add hex string conversion methods to WolfCrypt class

[cconlon]

This PR wraps native Base16_Encode() and Base16_Decode() for in WolfCrypt.toHexString() and WolfCrypt.hexStringToByteArray() methods. Includes Base16Enabled() feature check and JUnit tests.

public static String toHexString(byte[] data);
public static byte[] hexStringToByteArray(String hexStr);

The wolfSSL native APIs above require WOLFSSL_BASE16 to be defined, but since --enable-jni already defines OPENSSL_EXTRA, which automatically defines WOLFSSL_BASE16, users shouldn't need to add anything else to native wolfSSL configure.

[Copilot]

Pull request overview

This PR adds hexadecimal string conversion capabilities to the WolfCrypt class by wrapping native wolfSSL Base16 encoding/decoding functions. The implementation includes proper feature detection, comprehensive error handling, and extensive test coverage.

• Adds toHexString() method to convert byte arrays to hexadecimal strings
• Adds hexStringToByteArray() method to convert hexadecimal strings back to byte arrays
• Includes Base16Enabled() feature detection method

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/main/java/com/wolfssl/wolfcrypt/WolfCrypt.java	Adds public API methods for hex conversion with proper validation and error handling
jni/jni_wolfcrypt.c	Implements JNI native methods with overflow protection, memory management, and error handling
jni/include/com_wolfssl_wolfcrypt_WolfCrypt.h	Declares JNI function signatures for new native methods
src/test/java/com/wolfssl/wolfcrypt/test/WolfCryptTest.java	Provides comprehensive test coverage including edge cases, thread safety, and known test vectors
src/test/java/com/wolfssl/wolfcrypt/test/WolfCryptTestSuite.java	Registers new test class in the test suite

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