Flip ADK CLI to be ESM native instead of CommonJS

[kalenkevich]

Description

This PR introduces enhanced control over how agent files are loaded and compiled in the ADK CLI. It adds support for specifying whether to compile or bundle agent code and allows explicit definition of the module type (ESM/CJS). This helps in handling different project setups and ensures better compatibility, particularly with ESM projects.

Key Changes:

New CLI Flags:

• --compile [boolean]: Controls whether to compile TS agent files (default: true).
• --bundle [boolean]: Controls whether to bundle agent files (default: true).
• --file_type : Explicitly sets the module type (cjs or esm) for files to run or load (via npx adk run | web | api_server).

Enhanced Agent Loading:

AgentFile class in dev/src/utils/agent_loader.ts updated to handle compilation and bundling options.
Added logic to automatically detect module type from file extensions (.mjs, .cjs) or package.json.
Added esbuild-shim-plugin to handle shims during bundling.

Enabled Debug with ADK CLI run command:

While working with ESM .js/.ts files you can run agent without file compile and bundle: npx adk run ./agent.ts --compile=false --bundle=false. That allows to load and debug original files.

Example of the VSCode launch.json config for debug:

{
      "name": "Debug: ADK agent",
      "type": "node",
      "request": "launch",
      "runtimeExecutable": "npx",
      "runtimeArgs": [
        "@google/adk-devtools",
        "run",
        "./src/agent.ts",
        "--compile=false",
        "--bundle=false"
      ],
      "console": "integratedTerminal",
      "skipFiles": ["<node_internals>/**"],
      "env": {
        "GOOGLE_GENAI_API_KEY": "<your key>"
      }
    }

Resolves:

#108
#76
#77