Tests: Add EdDSA/XDH default and compatibility suites; unify capability gating

[ariawisp]

What

• Add default tests for EdDSA (Ed25519/Ed448) and XDH (X25519/X448).
• Add compatibility tests for EdDSA/XDH across providers.
• Move provider capability checks into support.kt (single place), remove redundant per-test gating.
• Update generator to include new test classes.
• No CI/test runner changes in this PR.

Why

• Ensure consistent coverage for new algorithms and consolidate gating logic for maintainability.

Notes

• Depends on Core APIs (EdDSA/XDH) — blocked by PR Core: Add EdDSA and XDH algorithm interfaces #109.
• Will run against available providers; tests are gated where algorithms or curves are unsupported.
• JS/browser runner remains as in main (no WTR/Karma edits here).