core: Add specific signals type hinting

[yotamN]

Classes with message listeners are:

• [x] Script
• [x] Session
• [ ] Bus
• [x] Device
• [x] DeviceManager
• [x] PortalService
• [x] Compiler

[yotamN]

Bus is the only class that I haven't add a specific handler, I don't think it's a blocker as it's already vastly better.