Improve project settings page (leftovers)

What does this MR do?

ce: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/26754

Part of larger MR https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/10318

This is the leftover changes. They include:

• Includes QA updates from https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/10375 in a separate commit

• limit width of Project name to input-md (240px) (this exact value was ux suggestion/requirement, but not actually possible using those classes. Instead we've matched what was approved for the group settings so it can be DRYd.)

• limit width of Project tags and project description to input-xl (560px) (this exact value was same as above)

• reduce spacing between section dividers to 24px (top & bottom margin)

• move ‘Export project’ section into the ‘Advanced’ section (as indicated)

• remove the 'Project name' input from the Rename repository section (duplicate of the same input in the Naming section on top)

• change the title of 'Rename repository' to 'Change path'

What are the relevant issue numbers?

Related to https://gitlab.com/gitlab-org/gitlab-ce/issues/49738

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated via this MR
• Documentation reviewed by technical writer or follow-up review issue created
• Tests added for this feature/bug
• Tested in all supported browsers
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides
• Link to e2e tests MR added if this MR has Requires e2e tests label. See the Test Planning Process.
• EE specific content should be in the top level /ee folder
• For a paid feature, have we considered GitLab.com plans, how it works for groups, and is there a design for promoting it to users who aren't on the correct plan?
• Security reports checked/validated by reviewer