Utilize Vulnerabilities::Statistic model for stats on GraphQL API

ee/app/graphql/ee/types/project_type.rb

@@ -26,11 +26,7 @@ module EE
 
         field :vulnerability_severities_count, ::Types::VulnerabilitySeveritiesCountType, null: true,
                description: 'Counts for each severity of vulnerability of the project',
-               resolve: -> (obj, _args, ctx) do
-                 Hash.new(0).merge(
-                   obj.vulnerabilities.with_states([:detected, :confirmed]).counts_by_severity
-                 )
-               end
+               resolve: -> (obj, *) { obj.vulnerability_statistic || Hash.new(0) }
 
         field :requirement, ::Types::RequirementsManagement::RequirementType, null: true,
               description: 'Find a single requirement. Available only when feature flag `requirements_management` is enabled.',

ee/spec/requests/api/graphql/project/vulnerability_severities_count_spec.rb

@@ -5,10 +5,7 @@ require 'spec_helper'
 RSpec.describe 'Query.project(fullPath).vulnerabilitySeveritiesCount' do
   let_it_be(:project) { create(:project) }
   let_it_be(:user) { create(:user) }
-  let_it_be(:confirmed_vulnerability) { create(:vulnerability, :confirmed, :high, project: project) }
-  let_it_be(:detected_vulnerability) { create(:vulnerability, :detected, :high, project: project) }
-  let_it_be(:resolved_vulnerability) { create(:vulnerability, :resolved, :high, project: project) }
-  let_it_be(:dismissed_vulnerabilities) { create(:vulnerability, :dismissed, :high, project: project) }
+  let_it_be(:statistic) { create(:vulnerability_statistic, :d, project: project) }
 
   let_it_be(:query) do
     %(
@@ -33,6 +30,6 @@ RSpec.describe 'Query.project(fullPath).vulnerabilitySeveritiesCount' do
   it "returns counts for each severity of the project's detected or confirmed vulnerabilities" do
     high_count = subject.dig('data', 'project', 'vulnerabilitySeveritiesCount', 'high')
 
-    expect(high_count).to be(2)
+    expect(high_count).to be(statistic.high)
   end
 end