Fixes #14730 - Only search host proxies explicitly

When searching hosts with free text in a taxonomy scope, if the taxonomy
has "all smart proxies" associated, it leads to scoped search generating
an incorrect scope which causes an invalid query:
`SELECT smart_proxies.id FROM "smart_proxies" "puppet_ca_proxies_hosts"`...

Fixes #14190 - consistent api output and search options

fixes #14434 - refactor tokens into concern from observer

rails-observers is still required via audited, but this removes the
usage in Foreman itself and unifies token-related code.

Fixes #3582 - Parameters on subnets

Fixes #13937 - search by domain parameters searches on primary_interface

Fixes #13348 - Allow searching of all hosts managed by a smart proxy

fixes #13236 - apply power operations to several hosts at once

This commit adds the ability to select multiple hosts and apply power operations
(reboot, shutdown, boot) to them.

Fixes #12891 - search_by_params and search_by_user for host return correct results

fixes #12194 - join fact tables multiple times for each search term

scoped_search usually generates a new inner join for each search term
when searching through a key/value table layout to correctly search for
hosts via multiple facts. Since the change to ext_method in 3f8e6c33, a...

fixes #12458 - escape values in fact searches to prevent SQL injection