feat(runtime): add runtime API discovery and call endpoints (incl. relay chain)

[F-OBrien]

Summary

This PR adds full support for runtime API discovery and call endpoints.

New endpoints

• GET /runtime/apis
• GET /runtime/apis/{apiId}
• POST /runtime/apis/{apiId}/{methodId}
• GET /rc/runtime/apis
• GET /rc/runtime/apis/{apiId}
• POST /rc/runtime/apis/{apiId}/{methodId}

What this PR adds

• New runtime API controllers/services for standard and relay-chain (rc) paths.
• Runtime metadata parsing for API/method discovery with method input/output typing.
• Runtime API invocation with named JSON parameters.
• Parameter validation/normalization:
  • accepts method arg names and arg{index} aliases
  • supports omitted/null for Option<T> inputs
  • returns clear errors for unknown/missing params or unknown API/method names
• Response type additions for runtime API summaries, details, and call results.
• Chain config updates to enable RuntimeApis and RcRuntimeApis where runtime
  endpoints are already available.
• OpenAPI v1 and v2 updates for new paths and schemas (including generic JSON
  result shape for runtime API call outputs).

Validation

• Added unit tests for runtime API service behavior

Release notes

• Feature: expose runtime API metadata and and call endpoints for both primary
  and relay-chain contexts.