Fixes #22529 - Refactor Template rendering to use a proper rendering service (#5683)

Fixes #21120 - orchestration tasks are added only once (#5079)

Refs #22164 - use cheaper FactoryBot methods

• Refs #22164 - FactoryBot.build -> FactoryBot.build_stubbed

• Refs #22164 - FactoryBot.create -> FactoryBot.build

in
- test/unit/*
- test/models/shared/taxonomies_base_test.rb
- test/controllers/hosts_controller_test.rb

Fixes #21424 - use factory_bot_rails

fixes #16557 - move tests into modern Rails layout

Models, controllers, mailers and helpers are now in test/ subdirs
matching app/ subdirs. Service, miscellaneous and old test/lib/ tests
are now in test/unit/ separated from models, which obsoletes the custom...

Fixes #16439 - Don't fail recreate if DNS is ok

If rebuilding a host and DNS is not "feasible" we don't want to fail
that host but rather recreate what's currently feasible.

If a DNS record is still valid we don't want to fail that host but
rather take the still valid entry.

fixes #15590 - ipv6 tftp orchestration

Fixes #12634 - New HW Model flag pxe_loader

Implementation of

https://github.com/theforeman/rfcs/blob/master/text/0001-PXE-Booting-UEFI.md

In short, new host/hostgroup flag PXE loader is added to specify TFTP
DHCP filename and Foreman now orchestrates all PXE-capable templates...

fixes #15709 - fix SuSE mediapath in PXELinux templates

fixes #15635 - tests for dns orchestration