Introduce ResourceSets to make loading of resource files more flexible

This MR introduces so called ResourceSets that allow loading Kubernetes manifests either via ConfigMap or from the file system.

Closes #240 (closed)

theodolite/examples/operator/example-benchmark.yaml

@@ -21,7 +21,7 @@ spec:
           properties:
             loadGenMaxRecords: "15000"
   kafkaConfig:
-    bootstrapServer: "localhost:9092" # "theodolite-cp-kafka:9092"
+    bootstrapServer: "theodolite-cp-kafka:9092"
     topics:
       - name: "input"
         numPartitions: 40