feat: hook into the Fluttium testing process

[wolfenrain]

Description

Fluttium already supports custom actions, allowing developers to write their own actions for their own applications or create generic ones. But there is still no way for them to know when a test is starting or when it is done or when it fails.

It would be quite useful if we can somehow allow them to register, aside from an action, a sort of Fluttium extension. This extension would be able to hook into different parts of the testing process to provide more functionality that wouldn't fit in a custom action.

Let's say you want to capture system level key events and emit them downwards into your app, currently that isn't possible with Fluttium and Fluttium would never support that natively as it it would be specific to only desktop platforms, which does not fit with Fluttium's idea of multi-platform features only. But it would also not make sense to have an action for it because then the developer would have to constantly add such an action to the top of each of their flow files.

But if we have an "extension" on Fluttium that is registered to the running process than that can handle this without the developer having to set anything up in the flow files.

Requirements

• Allow developers to extend's Fluttium and hooking into the process flow.
• Define what kind events/parts we should expose to the developers

Additional Context

None as of yet.