MEDIUM: spoe/rules: Process "send-spoe-group" action

MEDIUM: spoe/rules: Process "send-spoe-group" action

The messages processing is done using existing functions. So here, the main task
is to find the SPOE engine to use. To do so, we loop on all filter instances
attached to the stream. For each, we check if it is a SPOE filter and, if yes,
if its name is the one used to declare the "send-spoe-group" action.

We also take care to return an error if the action processing is interrupted by
HAProxy (because of a timeout or an error at the HAProxy level). This is done by
checking if the flag ACT_FLAG_FINAL is set.

The function spoe_send_group is the action_ptr callback ot