fix: Properly genericize engine option of JsonRpcServer constructor

[rekmarks]

Explanation

The engine option of the JsonRpcServer constructor param was improperly genericized and didn't actually work in practice. This is now fixed.

References

N/A

Checklist

• I've updated the test suite for new or updated code as appropriate
• I've updated documentation (JSDoc, Markdown, etc.) for new or updated code as appropriate
• I've communicated my changes to consumers by updating changelogs for packages I've changed, highlighting breaking changes as necessary
• I've prepared draft pull requests for clients and consumer packages to resolve any breaking changes

---

Note

Properly types JsonRpcServer constructor engine option using ReturnType<typeof JsonRpcEngineV2.create<...>> and updates the changelog entry.

• Types:
  • Update JsonRpcServer Options.engine to ReturnType<typeof JsonRpcEngineV2.create<Middleware>> for correct generics in src/v2/JsonRpcServer.ts.
• Docs:
  • Add PR reference #7032 to JsonRpcEngineV2 entry in packages/json-rpc-engine/CHANGELOG.md.

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[Gudahtt]

LGTM!