JDK: Implement EdDSA and XDH; RAW key wrap/unwrap helper; wire provider

[ariawisp]

What

• Add JDK implementations for EdDSA (Ed25519/Ed448) and XDH (X25519/X448).
• Introduce a small helper for RAW/SPKI/PKCS#8 wrap/unwrap.
• Wire new algorithms in JdkCryptographyProvider.
• No CI/build/test changes in this PR.
• Use shared base helper unwrapSubjectPublicKeyInfo(Set,ObjectIdentifier) for SPKI decoding; remove JDK-local SPKI unwrap helper (keep minimal PKCS#8 helper for RAW private keys).

Why

• Provide JVM support for EdDSA/XDH behind the new core APIs; enables early testing and adoption on JDK.

Notes

• Availability: XDH available since JDK 11; EdDSA generally since JDK 15.
• Depends on Core APIs (EdDSA/XDH) — blocked by PR Core: Add EdDSA and XDH algorithm interfaces #109.
• Optional DER/PEM support can follow once ASN.1 changes merge (PR ASN.1: RFC 8410 OIDs, ABSENT params, Unknown key preservation, SEQUENCE OF support #108); this PR focuses on provider implementation and wiring.