* feat(host-rules): support disabling hosts

Adds “enabled” to the list of recognized configuration options for hostRules. A host or domain can be disabled by setting `”enabled”: false` within the host rule. Also added presets :disabledHost() and :disableDomain().

* docs

* tests

* Update configuration-options.md

* fixes

If defined in env, this will bypass pom checks and instead rely on the metadata alone.

Related: #6591, #6572

Co-authored-by: Jamie Magee <jamie.magee@gmail.com>

This reverts commit 0345b40a.

null = this lookup returned nothing last time
undefined = no cached result found