Add resource type for threads (vertical scaling)

Will fix #269 (closed).

• Kafka Streams
• Flink
• Hazelcast Jet
• Beam/Flink
• Beam/Samza

Might be backported as feature previews to 0.8.x (see #403 (closed)).

theodolite-benchmarks/definitions/uc1-beam-flink/resources/flink-configuration-configmap.yaml

@@ -7,6 +7,7 @@ metadata:
 data:
   flink-conf.yaml: |+
     jobmanager.rpc.address: flink-jobmanager
+    taskmanager.numberOfTaskSlots: 1
     blob.server.port: 6124
     jobmanager.rpc.port: 6123
     taskmanager.rpc.port: 6122