Event support and general console protocol cleanup

[HadrienG2]

• Implemented basic support for awaiting UEFI events.
• Made Handle and Event different newtypes of void* so assigning one to the other is an error
  • No ergonomics are lost since from the user's point of view these are opaque types anyway.
• Clarified the stateful nature of Pointer::get_state
• Made text input protocol more consistent with pointer protocol
• Improved documentation and method ordering of text output protocol

[HadrienG2]

So... with the Status discussion delayed, are you satisfied with the general state of this MR?

[GabrielMajeri]

Yes, it's good. I haven't used events a lot with UEFI, so we might end up refactoring the API in the future.