[Task]: Remove CI and CD checks from GitHub workflows

[rshamunov]

What needs to happen?

CI/CD workflows in GitHub replaced by Cloud Build triggers. Remove files from .github/workflows/ after CI/CD integration is completed:
playground_examples_cd.yml
playground_examples_cd_reusable.yml
playground_examples_ci.yml
playground_examples_ci_reusable.yml

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