[examples] Convert all examples to Maven projects

[chernser]

Description

There are some example projects that use Gradle what add some maintenance complexity.

Task:

• Convert all gradle project in examples/ folder to maven
• Do not use any maven wrapper because it pulls binary jar into git (what is wrong)
• Remove all gradle related folders and files from these projects
• Update .github/workflows/build.yml accordingly
• Update .github/workflows/run_examples.yml accordingly

[chernser]

@polyglotAI-bot implement the task