Add antibot integration

I am not sure about the test here. /antibot needs to be requested via POST, to not get the cached page, but I did just expand the existing Functional test.

> One other thing @Berdir also mentioned is that there could be different thresholds per source there or even add configuration for antibot/honeypot triggers.

not per source automatically but only configurable. The idea is that the /antibot and also honeypot are much more likely to be hit accidentally by real users than some wordpress thing. There are for example bugs in antibot in case of empty multistep forms where you can click without a mouse movement. So there is an argument to have higher thresholds for that.

Also, the route based approach is a workaround due to antibot not having a hook/event.