Remove welcome onboarding step from non SaaS

What does this MR do and why?

What?

• Removes welcome page from onboarding(registration) process for all except ee + SaaS setup. Users will now either be sent to the dashboard_projects_path, a group/project activity path(if invite), or a stored location. To accomplish this, we needed to copy the welcome controller's redirection after update logic back one step to the sign up submission area.
• reduce complexity and get to a place of not splitting the welcome controller and logic between ce and ee.
  • moving the welcome controller fully to ee and moving the route to only be on ee will be done in the next MR(!129528 (merged)) in an effort to make a smaller MR
• resolve .rubocop_todo/rspec/context_wording.yml items in a few files

Why?

welcome/onboarding only has value in SaaS where marketing concepts like trials are in play, see #411858 (comment 1512834991) for more of the why.

note I didn't find any docs that would need an update.

Screenshots or screen recordings

No UI changes, merely removal of every type of GitLab having to at least fill would the welcome form.

How to set up and validate locally

Non SaaS

1. Ensure GDK is not setup to simulate SaaS
2. Disable check_namespace_plan in rails console
   • ApplicationSetting.first.update(check_namespace_plan: false)
3. Restart GDK
4. Register as a new user.
5. After registration, and any confirmation steps, you should land on the dashboard/projects page.
   • compare this to master behavior where you will land on the welcome form first instead.

SaaS (no behavior change)

1. Ensure GDK is setup to simulate SaaS
2. Enable check_namespace_plan in rails console
   • ApplicationSetting.first.update(check_namespace_plan: true)
3. Restart GDK
4. Register as a new user.
5. After registration, and any confirmation steps, you should land on the welcome page(in onboarding).

note You can get the new user confirmation token, if you setup is set that way, by running the below in rails console

• Rails.application.routes.url_helpers.user_confirmation_path(confirmation_token: User.last.confirmation_token)

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 #411858 (closed)