Resolve "Create new project: Re-add project name field"

What does this MR do?

Re-adds the 'Project name' field to the 'Create new project' page and automatically generates the 'Project slug' as the user types the name. The automatically generated slug is converted to lowercase and dash-delimited. The 'Project slug' input field is autofocused on page load and remains editable. Input field 'Project path' is renamed to 'Project URL'.

project-slug

The related EE MR is https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/7279

What are the relevant issue numbers?

#2934 (closed)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• Tests added for this feature/bug
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides

Closes #2934 (closed)