Rewrite all examples to use language-specific build systems and environments

[izmalk]

Problem to Solve

We don't want to have our examples as Bazel project. Instead, we should use native tools for every language we use.

Proposed Solution

For the whole repository, we should:

• Delete all Bazel files, including: WORKSPACE, BUILD in the root and all subdirectories, .bazelrc, .bazelversion.
• Rewrite README.md files with new instructions on how to build and use examples without Bazel.

Instead of Bazel we should use native tools and most predominant build systems / runtime environments if needed:

• Python: Python (using pip to install deps).
• JS: Node and npm (or yarn).
• Java: Maven and/or Gradle.