Meta to implement the CommandsHandler architecture initially described in https://docs.google.com/presentation/d/1iIcVlQkNPhTj7wos2WbGV-7EqK6Qbbd8Kay5OjvH3ck/edit#slide=id.gcdb79f24e4_0_6 and https://docs.google.com/document/d/1Of3ZhWIAwYXPezuG_hMpmTK7Nv1a9_E_VsnBWtD2nD8/edit#heading=h.fhzr3f7daxcl

The CommandsHandler architecture should allow to:

• reach any context relevant for either WebDriver BiDi or devtools (chrome window, content window, process, worker)
• spawn modules in any relevant layer (parent process, content process main thread, content process worker thread)
• support multiple sessions (eg one from WebDriver BiDi + one from DevTools)
• route commands from the parent process to any context
• intercept commands at any layer between the parent process and the destination
• persist and broadcast session data (eg list of events currently subscribed to)
• handle new contexts created during the session (eg new frame appearing)