Default RSA KeyPairGenerator params, null AlgorithmParameters for non-PSS, RSA exponent sanitization

[cconlon]

This PR includes three fixes:

• In KeyPairGenerator, set default RSA key size and parameters if the application has not explicitly set. We default to RSA 2048 for interop compatibility.
• In Signature, allow null AlgorithmParameterSpec to be passed in for non-PSS algorithms
• In KeyPairGenerator, add RSA exponent sanitization. Must be larger than 1 and odd.

JUnit tests are included for regression prevention.

This fixes some of the OpenJDK SunJCE RSA tests.

[Copilot]

Pull Request Overview

This PR enhances RSA key generation and signature handling in the WolfSSL JCE provider by implementing proper default parameter handling and input validation. The changes improve compatibility with OpenJDK SunJCE RSA tests.

• Set default RSA key generation parameters (2048-bit keys) when not explicitly initialized
• Allow null AlgorithmParameterSpec for non-PSS signature algorithms while rejecting non-null parameters
• Add RSA public exponent validation to ensure it's positive and odd

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
WolfCryptKeyPairGenerator.java	Adds default RSA parameters initialization and public exponent validation
WolfCryptSignature.java	Updates parameter handling to accept null for non-PSS algorithms
WolfCryptKeyPairGeneratorTest.java	Adds tests for default RSA key generation and invalid exponent validation
WolfCryptSignatureTest.java	Adds tests for null parameter handling in non-PSS signatures

---

_{Tip: Customize your code reviews with copilot-instructions.md. Create the file or learn how to get started.}