Upgrade to GitLab Styles 9

This contains upgrades RuboCop to 1.3.6 and RuboCop RSpec to 2.12.1. See gitlab-org/ruby/gems/gitlab-styles!119 (merged) for more details.

Notable changes here are:

1. Cops now get their namespace from all but the last and the first two components, rather than simply the last component. See https://github.com/rubocop/rubocop/pull/8490
2. There is no more TopLevelDescribe helper for Rubocop RSpec, it's now TopLevelGroup. See https://github.com/rubocop/rubocop-rspec/pull/977
3. RuboCop Rails now complains if db/schema.rb doesn't contain a schema.

For existing cops in our codebase, see !97518 (merged).

This MR contains two commits in an attempt to make it easier to review:

1. The initial upgrade, with deletions of db/schema.rb and ee/db/geo/schema.rb as these now cause a cop to error. This also sets NewCops: disable as we should enable any of these in gitlab-styles first: gitlab-org/ruby/gems/gitlab-styles#40 is a related issue.
2. Run bundle exec rake rubocop:todo:generate on the existing cops with new offenses (bundle exec rubocop --parallel --format offenses). See !96880 (comment 1086831683) for a partial list here.

The second commit is the one that's most likely to need to be updated as we go. The rest should be stable unless we add new cops.