Validate EC key sizes in KeyPairGenerator.initialize()

[cconlon]

This PR adds validation to EC KeyPairGenerator.initialize(int keysize) to only accept standard NIST key sizes (192, 224, 256, 384, 521 bits), matching SunEC and Bouncy Castle behavior. Invalid sizes now throw InvalidParameterException instead of being silently accepted.

For non-NIST curves (secp256k1, Brainpool, etc), users must use ECGenParameterSpec explicitly.

This fixes compatibility with SunJCE security/KeyAgreement/NegativeTest.java test.

[Copilot]

Pull Request Overview

This PR enhances EC key pair generation by adding validation to restrict KeyPairGenerator.initialize(int keysize) to standard NIST curve sizes (192, 224, 256, 384, 521 bits), matching SunEC and Bouncy Castle behavior. Invalid sizes now throw InvalidParameterException instead of being silently accepted.

Key changes:

• EC key sizes are validated and mapped to specific NIST curves (secp192r1, secp224r1, secp256r1, secp384r1, secp521r1)
• Non-NIST curves must now be requested explicitly via ECGenParameterSpec
• Test cases updated to work with bit sizes and validate the new exception behavior

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 6 comments.

File	Description
src/main/java/com/wolfssl/provider/jce/WolfCryptKeyPairGenerator.java	Adds EC key size validation with NIST curve mapping and availability checking in the initialize(int keysize) method
src/test/java/com/wolfssl/provider/jce/test/WolfCryptKeyPairGeneratorTest.java	Updates existing test to use bit sizes correctly and adds comprehensive new tests for invalid sizes, valid NIST curve mapping, and non-standard curve requirements

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