Geo migration specs are not running in CI

As we found out in #352150 (comment 860512411), because we don't have a rspec-ee migration geo job, the specs in ee/spec/migrations/geo didn't run in CI for a long while.

Copying my comment from the thread:

I took a look at https://gitlab.com/gitlab-org/gitlab/-/jobs/2154831080 for example, and I can see:

KNAPSACK_TEST_FILE_PATTERN: {ee/}spec/{bin,channels,config,db,dependencies,elastic,elastic_integration,experiments,events,factories,finders,frontend,graphql,haml_lint,helpers,initializers,javascripts,lib,metrics_server,models,policies,presenters,rack_servers,replicators,routing,rubocop,scripts,serializers,services,sidekiq,sidekiq_cluster,spam,support_specs,tasks,uploaders,validators,views,workers,tooling}{,/**/}*_spec.rb

This comes from scripts/rspec_helpers.sh, more specifically executing ./tooling/quality/test_level.rb with the job name, and we only have rspec-ee unit|integration|system geo jobs, but no migration one, despite not excluding the migrations specifically as we do in regular tests (i.e. with --tag ~level:migration), which results in no tests in ee/spec/migrations/geo/* running.

I think we want to add an extra rspec-ee migration geo job in order to get this working.

@kwiebers opened an initial MR at !82039 (closed) for this.