[benchmarking] Implement message listeners across appropriate modules

[lynchee-owo]

This does not add new features to user side, but only for benchmarking.

Ensure that all necessary message listeners are implemented in the correct components or modules within the WebWand architecture.

• Identify and document where each listener should reside based on their functionality. For example, openSidePanel might be in background/index.js, but others like runTask might be in a different part of the extension.
• Implement a simple response mechanism for each listener to confirm receipt of messages by sending back a "heard" message to the Python script.
• For each listener identified, develop the specific functionalities they need to execute. For example, storeAPIKey should securely store the received key, runTask should handle task execution, and fetchScreenshot should capture and send back a screenshot.

Note:
think about how to deal with the state manament.