Adds JavaScript validation for group path editing

What does this MR do?

• Prevents group_edit form submission when special characters are included in the new group name
• Enhances gl_field_errors to support this use case and be more re-usable.

Are there points in the code the reviewer needs to double check?

The implementation of validation is here: https://gitlab.com/gitlab-org/gitlab-ce/commit/73d997046cac376ccdbcaac6f183002bc19b9a1f

The rest of the diff for this MR is augmenting gl_field_errors

Why was this MR needed?

• Currently we allow submission and a 500 error is returned.

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• CHANGELOG entry added
• Documentation created/updated
• All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/23564, https://gitlab.com/gitlab-org/gitlab-ce/issues/19756, https://gitlab.com/gitlab-org/gitlab-ce/issues/19736, https://gitlab.com/gitlab-org/gitlab-ce/issues/23922