Add metrics for the new Check API

New metrics are necessary because the new API no longer wraps
an EPP flow, therefore does not get metrics for free.

Metrics include
 - An EventMetric for processing time
 - An IncrementableMetric for request count, with
   availability (available/reserved/registered) and
   pricing (standard/premium) fields

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=199708592

java/google/registry/monitoring/whitebox/WhiteboxModule.java

@@ -71,6 +71,11 @@ public class WhiteboxModule {
     return EppMetric.builderForRequest(requestLogId, clock);
   }
 
+  @Provides
+  static CheckApiMetric.Builder provideCheckApiMetricBuilder(Clock clock) {
+    return CheckApiMetric.builder(clock);
+  }
+
   @Provides
   @Named(QUEUE_BIGQUERY_STREAMING_METRICS)
   static Queue provideBigQueryStreamingMetricsQueue() {