MINOR: mux-h1: Add a idle expiration date on the H1 connection

MINOR: mux-h1: Add a idle expiration date on the H1 connection

An idle expiration date is added on the H1 connection with the function to
set it depending on connection state. First, there is no idle timeout on
backend connections, For idle frontend connections, the http-request or
keep-alive timeout are used depending on which timeout is defined and if it
is the first request or not. For embryonic connections, the http-request is
always used, if defined. For attached or shutted down connections, no idle
timeout is applied.

For now the idle expiration date is never set and the h1_set_idle_expiration
function remains unused.