Rework/sanitize parser hooks

[jerch]

Currently we expose custom hooks to CSI and OSC commands. Idea is to extend this to ESC and DCS commands as well. Furthermore the current interface needs some overhaul to land as stable in v4.

TODO:

• implement addEscHandler for public usage
• implement addDcsHandler for public usage
• review addCsiHandler, remove "experimental" badge
• review addOscHndler, remove "experimental" badge