Allow using actual HTTP monitors instead of emulating them in TCP monitors.
Doing this is not forward-compatible, ie octodns-ns1 cannot be downgraded to
a previous version that doesn't support modern HTTP monitors. It also doesn't
honor the http_version configuration because these monitors can only talk
HTTP/1.1.
Newly added support for subnet targeting using the Netfence Prefix filter
v0.0.5 - 2023-07-27 - Dynamic Subnets
http_version
configuration because these monitors can only talk HTTP/1.1.