Only load vulnerability related records when actually exporting

Without this change, the `with_findings_scanner_identifiers_and_notes`
scope eager loads all the supporting models for the serialisation when
we are enqueing the export and will not use this data. This also occurs
before the inner `enumerator` is used, meaning the batch size is too
large to actually carry out.

Changelog: fixed
EE: true

ee/app/services/vulnerability_exports/export_service.rb

@@ -179,7 +179,6 @@ def vulnerability_reads_scope
         exportable.vulnerability_reads.unarchived.order_traversal_ids_asc
       else
         Security::VulnerabilityReadsFinder.new(exportable).execute
-                                          .with_findings_scanner_identifiers_and_notes
                                           .order_detected_at_asc
       end
     end

ee/spec/services/vulnerability_exports/export_service_spec.rb

@@ -36,6 +36,14 @@
       expect(csv['Vulnerability']).to match_array(expected_titles)
       expect(csv['Status']).to match_array(expected_states)
     end
+
+    it 'does not have an N+1' do
+      query_count = ActiveRecord::QueryRecorder.new do
+        export_segment
+      end.count
+
+      expect(query_count).to eq(expected_export_query_count)
+    end
   end
 
   describe '#export_segment' do
@@ -65,6 +73,7 @@
     context 'when exporting a group' do
       let(:expected_titles) { [vulnerability_1.title, vulnerability_2.title, vulnerability_3.title] }
       let(:expected_states) { [vulnerability_1.state, vulnerability_2.state, vulnerability_3.state] }
+      let(:expected_export_query_count) { 21 }
 
       it_behaves_like 'generates an exported segment'
     end
@@ -82,6 +91,7 @@
 
       let(:expected_titles) { [vulnerability_2.title, vulnerability_3.title] }
       let(:expected_states) { [vulnerability_2.state, vulnerability_3.state] }
+      let(:expected_export_query_count) { 21 }
 
       it_behaves_like 'generates an exported segment'
     end
@@ -255,6 +265,14 @@
         export
       end
 
+      it 'does not attempt to preload the export data unnecessarily' do
+        query_count = ActiveRecord::QueryRecorder.new do
+          export
+        end.count
+
+        expect(query_count).to eq(12)
+      end
+
       it 'sets organization_id appropriately' do
         expect { export }.to change { ::Vulnerabilities::Export::Part.count }.from(0).to(2)