Cdp full async

[francisbouvier]

This PR ensure that all read and write I/O are done asynchronously:

• on the readCbk the next read is sent to the kernel before doing the actual command work (so both are concurrent)
• on the write part the sendSync command was removed in favor of the sendAsync

[krichprollsch]

The end of a connection results always with a error.FileDescriptorNotASocket error

$ ./zig-out/bin/browsercore
info(server): Listening on: 127.0.0.1:3245...
info(server): accepting new conn...
info(server): close cmd, closing conn...
info(server): accepting new conn...
error(server): Server error: error.FileDescriptorNotASocket