Setup ClickHouse on CI

This change updates the pipeline settings to run a separate job for
RSpec tests tagged with click_house.

spec/lib/gitlab/database/click_house_client_spec.rb

@@ -124,4 +124,18 @@ def format_row(event)
       expect(result).to eq([{ 'value' => 1 }])
     end
   end
+
+  describe 'querying data', :click_house do
+    around do |example|
+      with_net_connect_allowed do
+        example.run
+      end
+    end
+
+    it 'returns data from the DB' do
+      result = Gitlab::ClickHouse::Client.execute("SELECT 1 AS value", :main)
+
+      expect(result).to eq([{ 'value' => 1 }])
+    end
+  end
 end