More comprehensive implementation of v1_listener

[erikziyunchi]

For now, the WATM with v1_listener Role is still in a PoC stage where it maps all accepted connections with one communication pipe to the host program. Will need a comprehensive implementation for it alongside with more full v1 designs.

[gaukas]

Once we publish v0, I think it will be a good time for us to settle on the final (or pre-final) specs for v1, including all WATM APIs and WATM capabilities. The design/implementation details could be decided along as the dev proceed.