Converge request user roles to match API and UI

[kbrock]

FOLLOWUP:

• Change request_controller special privileges manageiq-api#447 change identifier in tests only
• use request_admin_user manageiq-ui-classic#4487 uses helper method

We introduced feature miq_request_superadmin in f6c02e8 / #17444
The feature miq_request_approval already existed.
Merging the 2 together.

This fixes an inconsistency between API and UI
The issue existed before this feature was introduced
so this works with #17444 to fix the BZ

https://bugzilla.redhat.com/show_bug.cgi?id=1608554

[kbrock]

@jrafanie and @gtanzillo This pushes us more towards using *_admin_user? type methods that you both like.

I do have a followup that will remove the ambiguous .admin_user? #17850
I've already removed references to admin_user? in all repos.

[miq-bot]

Checked commit kbrock@9a63e12 with ruby 2.3.3, rubocop 0.52.1, haml-lint 0.20.0, and yamllint 1.10.0
1 file checked, 0 offenses detected
Everything looks fine. 👍

[jrafanie]

@kbrock did you try to use the new recreation environment from the bz? I'm curious if this change fixes the api not bring back requests for approvers

[kbrock]

@jrafanie I need to backport this stuff to that environment to check it. This backport effort is non-trivial. Since we want to make this change regardless, can we just do this and then followup if it doesn't fix all the issues?