Support for Envoy gRPC HTTP/1.1 bridge

[ikhoon]

To send gRPC response over HTTP/1, Armeria uses chunked transfer-encoding to deliver gRPC response trailers.
https://datatracker.ietf.org/doc/html/rfc9112#section-7.1.2.
This is non-standard for gRPC and some legacy L7 proxy server may not handle trailers in chucked encoding correctly.

A more HTTP/1-friendly approach alternative is gRPC HTTP/1 bridge specification defined in Envoy. This specification buffers the HTTP/2 response, copies the gRPC trailers into response headers, and then converts it into an HTTP/1 response. This improves compatibility with legacy systems, but it disables real time streaming due to buffering.

Since both approaches have trade-offs, I propose introducing an option so users can choose the appropriate mode for their network environment.

GrpcService
  .builder()
  .enableEnvoyHttp1Bridge(boolean)