Update Kafka mixin to use React based panels (#1129)

* Move existing dashboards to new subfolder

These dashboards all have and use older Angular based panels (graph and table-old)

* Add flattened json dashboards, all updated to use react based panels

* Add missing newline

* Fix lint-fmt issue

Author: Dasomeone

kafka-mixin/dashboards/connect-overview.json

@@ -1,7 +1,12 @@
-(import 'connect-overview.libsonnet') +
-(import 'kafka-overview.libsonnet') +
+// # Libsonnet dashboards targetting the correct Grafana schema. Outdated dashboards can be found in old-dashboards/
 (import 'kafka-lag-overview.libsonnet') +
-(import 'kafka-topics.libsonnet') +
-(import 'ksqldb-overview.libsonnet') +
-(import 'schema-registry-overview.libsonnet') +
-(import 'zookeeper-overview.libsonnet')
+(import 'zookeeper-overview.libsonnet') +
+{
+  grafanaDashboards+:: {
+    'connect-overview.json': (import 'connect-overview.json'),
+    'kafka-ksqldb-overview.json': (import 'kafka-ksqldb-overview.json'),
+    'kafka-overview.json': (import 'kafka-overview.json'),
+    'kafka-topics.json': (import 'kafka-topics.json'),
+    'schema-registry-overview.json': (import 'schema-registry-overview.json'),
+  },
+}