Add HTTP/1.1 handler support to Node.js endpoint

[nikrooz]

Some Node.js frameworks and libraries only accept HTTP/1.1 request listeners, so integrating Restate with them means going through the fetch handler and converting it back to a Node listener.

This isn't strictly needed, that conversion works fin, but having a native HTTP/1.1 handler makes those integrations a bit more straightforward. Totally fine if we prefer not to expand the API surface.

• Add http1Handler() and handler() methods to RestateEndpoint, alongside the existing http2Handler().
• http1Handler() returns a handler typed for http.createServer(). It defaults to REQUEST_RESPONSE protocol mode; pass { bidirectional: true } to use BIDI_STREAM.
• handler() returns an overloaded callable that auto-detects HTTP version per request: HTTP/2+ uses BIDI_STREAM, HTTP/1.1 uses REQUEST_RESPONSE by default. The bidirectional option is tri-state: true forces BIDI_STREAM for all, false forces REQUEST_RESPONSE for all, undefined auto-detects.
• createEndpointHandler() now returns the unified handler(), accepting a new NodeEndpointOptions type with the bidirectional option.
• Internally, the handler is split into nodeHttp1Handler / nodeHttp2Handler typed wrappers over a shared nodeHandlerImpl, separating HTTP transport types from protocol mode.
• Add HTTP/1.1 example (greeter_http1.ts) and integration tests covering both request-response and bidirectional modes using testcontainers with use_http_11: true.

[github-actions]

Test Results

  7 files  ±0    7 suites  ±0   3m 21s ⏱️ +16s
 49 tests ±0   49 ✅ ±0  0 💤 ±0  0 ❌ ±0 
210 runs  ±0  210 ✅ ±0  0 💤 ±0  0 ❌ ±0 

Results for commit 887fa32. ± Comparison against base commit e292abc.