Fixes #18952 - fix destroy of host without owner

The notifications failure caused the host not being deleted.
I don't think the notifications should interfere with the core
functionality of the objects.

fixes #18681 - moves polymorphic subject into notification object

also adds host build, destroyed and missing owner UI notifications

Fixes #14013 - add a setting for default owner of new hosts

Refs #17272 - fix sql condition

1==1 is not a valid SQL condition.

Fixes #17272 - Fixed Searches on parameters with !=

Fixes #16752 - Extract template code from Host::Managed

Host::Managed contains a lot of code related with determining the
template that a host should have. Other Host objects such as
Host::Discovered might need that logic, without becoming a
Host::Managed....

Fixes #12547 - Added validators to interger fields

With this commit, instead of postgresql exception it will
show proper validation message for interger fields.

fixes #18024 - add 'image' search field to hosts

fixes #17574, #17364 - update scoped_search to 4.x

scoped_search's sort() now accepts a replacement for params which is
filtered in an overridden Foreman sort helper, permitting additional
parameters used in Foreman's index pages.

Replaces :in and :alias in search definitions with preferred keywords.

Fixes #14688 - Power status visible on hosts index page