Bluetooth: Host: Introduce BT_CONN_PARAM_ANY

Some controllers support additional connection parameter ranges
beyond what is described in the specification. Enabling this new option
allows the application to set any value to all connection parameters.
Tbe Host will perform no limits nor consistency checks on any of the
connection parameters (conn interval min and max, latency and timeou).
However, the Host will still use numerical comparisons between the
min and max connection intervals in order to verify whether the
desired parameters have been established in the connection.

Signed-off-by: Carles Cufi <carles.cufi@nordicsemi.no>