Introduce average resampler support

Fixes #526

Entire-Checkpoint: 893a1de325b5

api/schema.graphqls

@@ -250,6 +250,12 @@ type TimeWeights {
   coreHours: [NullableFloat!]!
 }
 
+enum ResampleAlgo {
+  LTTB
+  AVERAGE
+  SIMPLE
+}
+
 enum Aggregate {
   USER
   PROJECT
@@ -340,6 +346,7 @@ type Query {
     metrics: [String!]
     scopes: [MetricScope!]
     resolution: Int
+    resampleAlgo: ResampleAlgo
   ): [JobMetricWithName!]!
 
   jobStats(id: ID!, metrics: [String!]): [NamedStats!]!
@@ -399,6 +406,7 @@ type Query {
     to: Time!
     page: PageRequest
     resolution: Int
+    resampleAlgo: ResampleAlgo
   ): NodesResultList!
 
   clusterMetrics(