Add GitLab Environment Toolkit service ping metric

config/metrics/license/20240327160214_gitlab_environment_toolkit.yml

+---
+key_path: gitlab_environment_toolkit
+description: Is the instance provisioned with the Gitlab Environment Toolkit
+product_section: analytics
+product_stage: analytics
+product_group: analytics_instrumentation
+value_type: boolean
+status: active
+milestone: "17.0"
+introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/148077
+time_frame: none
+data_source: database
+data_category: optional
+instrumentation_class: GitlabEnvironmentToolkitMetric
+performance_indicator_type: []
+distribution:
+- ee
+tier:
+- premium
+- ultimate

lib/gitlab/usage/metrics/instrumentations/gitlab_environment_toolkit_metric.rb

+# frozen_string_literal: true
+
+module Gitlab
+  module Usage
+    module Metrics
+      module Instrumentations
+        class GitlabEnvironmentToolkitMetric < GenericMetric
+          value do
+            Gitlab::CurrentSettings.gitlab_environment_toolkit_instance
+          end
+        end
+      end
+    end
+  end
+end

spec/lib/gitlab/usage/metrics/instrumentations/gitlab_environment_toolkit_metric_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe Gitlab::Usage::Metrics::Instrumentations::GitlabEnvironmentToolkitMetric, feature_category: :service_ping do
+  let(:expected_value) { Gitlab::CurrentSettings.gitlab_environment_toolkit_instance }
+
+  it_behaves_like 'a correct instrumented metric value', { time_frame: 'none' }
+end