[Task]: Remove NotificationManager frontend class, submit CodeRunner's updates to ToastNotifier outside of widgets

[alexeyinkin]

What needs to happen?

Remove NotificationManager frontend class, submit CodeRunner's updates to ToastNotifier outside of widgets.

Issue Priority

Priority: 3 (nice-to-have improvement)

Issue Components

• Component: Python SDK
• Component: Java SDK
• Component: Go SDK
• Component: Typescript SDK
• Component: IO connector
• Component: Beam examples
• Component: Beam playground
• Component: Beam katas
• Component: Website
• Component: Spark Runner
• Component: Flink Runner
• Component: Samza Runner
• Component: Twister2 Runner
• Component: Hazelcast Jet Runner
• Component: Google Cloud Dataflow Runner

[alexeyinkin]

.take-issue