Clean up and delete the code related to the old provider forms

[skateman]

✂️ 🚽 🔥 💧 🦛

ManageIQ/manageiq#18818

[himdel]

EmsCommon mixin - new and edit are also dead now, right?

it also has all the retrieve_ methods used to populate selects in the old form - provider regions, openstack api versions, security protocols.

EDIT: new/edit are still alive and kicking

[himdel]

Tested infra, cloud, phinfra, container, network providers, * storage managers, and (partially, no providers) configuration.
Looks like new/edit still work just fine wherever available, the same goes for textual summaries, overview screens, show_list and topologies.

I think this is good to go 👍

(Just the EmsCommon#retrieve_ methods please, if you agree? :))

[skateman]

Yeah, the edit and new routes are still drawing the views that contain the forms. Deleting the set_form_vars and all its children, like retrieve_*...

[chessbyte]

typo: EmsCloud

[miq-bot]

Checked commit skateman@775acdd with ruby 2.5.7, rubocop 0.69.0, haml-lint 0.28.0, and yamllint
24 files checked, 1 offense detected

**

• 💣 💥 🔥 🚒 - Linter/Haml - Linter::Haml STDERR:

warning: parser/current is loading parser/ruby25, which recognizes
warning: 2.5.8-compliant syntax, but you are running 2.5.7.
warning: please see https://github.com/whitequark/parser#compatibility-with-ruby-mri.