Add SSO registration flow feature specs

What does this MR do and why?

• Adds SSO coverage to all of our standard and trial feature specs for SaaS
• Attempts to maintain readability of this area(honor rubocop/cop/gitlab/rspec/avoid_setup.rb) and at the same time improve DRYness just a bit
  • see the first few sso_ test files we had go away and become integrated into the existing standard and trial flows.
  • see use of case_name to maintain readability when formatters are used when running the spec file like -f documentation

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #406651 (closed)