picobsd/tinyware has had this compact HTTPD server for a long time, and some people do use it. Move it out into usr.sbin in advance of any action being taken on picobsd.
This has been gated behind an HTTPD option defaulted to *off*, primarily for two reasons:
1.) This code likely needs a good audit, as it's been living off in picobsd land for a long time, and
2.) We don't currently ship an httpd and this may not be a welcome surprise.