Eng: Update Subgroup creation page

Summary

The goal of this issue is to update the subgroup creation experience seen below. Currently, the same design is used for when a user creates a parent level group and a subgroup with the only change being that the subgroup page has a string attached to the URL in the location bar and includes an option for the URL path that the subgroup should have.

Solution

We should update this page so it's clear that:

• we are creating a subgroup, and which group it is being created within
• we can choose which group that this subgroup will be created within
• we do not need most of the additional questions asked during the creation of parent-level groups (i.e. role, what this group will be used for, etc.)

Note we can reuse the updated design that's included in creating a project where the user is asked to select the parent level group before naming the project. The engineering work related to this effort can be found here #348191 (closed). In this issue, the user would be selecting the parent level group and then indicating they can create/name their subgroup.

Design

• #354530[02-new-subgroup-form.jpg]
• Figma specs

Changes required

• Remove the page where the user has two options: create a blank group or import an existing one. Direct the user straight to the create blank subgroup page
• Update the copy on the left side of the screen as indicated in the design
  • The import an existing group link links to the import subgroup page (example: /groups/new?parent_id=9908391#import-group-pane)
• Remove everything below Now, personalize your GitLab experience
• Change the wording from Group to Subgroup as indicated in the design