Disable writeHandler registration for net sockets and websockets by default

[tsegismont]

When a net socket is created, it registers a local consumer which address is given by io.vertx.core.net.NetSocket#writeHandlerID.

Similarly, when a websocket is created, it registers local consumers which addresses are given by io.vertx.core.http.WebSocketBase#binaryHandlerID and io.vertx.core.http.WebSocketBase#textHandlerID.

This puts some pressure on cluster managers when Vert.x is clustered, even if most users don't need the feature.

We shall disable write handlers registration by default (as we did for SockJS handler in vert-x3/vertx-web#1221).

This is a breaking (behavioral) change, but users will be able to switch the feature on with options.