[call-v3] Grab payload handling from registered method (#36017)

We were skipping reading a request payload, which led to a serialization failure, which led to UNIMPLEMENTED errors.

Closes #36017

COPYBARA_INTEGRATE_REVIEW=https://github.com/grpc/grpc/pull/36017 from ctiller:goodness 606545295f
PiperOrigin-RevId: 611254339

src/core/lib/surface/server.cc

@@ -1454,6 +1454,7 @@ void Server::ChannelData::InitCall(RefCountedPtr<CallSpineInterface> call) {
           if (registered_method == nullptr) {
             rm = server_->unregistered_request_matcher_.get();
           } else {
+            payload_handling = registered_method->payload_handling;
             rm = registered_method->matcher.get();
           }
           auto maybe_read_first_message = If(