Unify Handle/HandleRef behind a single trait.

[todo]

The fact I have to do this makes me think there's really a problem in the handle/handleref design. Maybe there should be a trait unifying Handle/HandleRef, and `Process` and co should be generic on those? That would allow me to call the functions on "borrowed lifetime-erased" handles.
This trait could probably be AsRef or Borrow. Ideally the generic types would be an internal implementation details and we'd just expose "Process" and "ProcessBorrowed" types through typedef/newtypes. Needs a lot of thought.

---

SunriseOS/loader/src/main.rs

Lines 222 to 232 in 7651488

	// TODO: Unify Handle/HandleRef behind a single trait.
	// BODY: The fact I have to do this makes me think there's really a
	// BODY: problem in the handle/handleref design. Maybe there should be a
	// BODY: trait unifying Handle/HandleRef, and `Process` and co should be
	// BODY: generic on those? That would allow me to call the functions on
	// BODY: "borrowed lifetime-erased" handles.
	// BODY:
	// BODY: This trait could probably be AsRef or Borrow. Ideally the
	// BODY: generic types would be an internal implementation details
	// BODY: and we'd just expose "Process" and "ProcessBorrowed" types
	// BODY: through typedef/newtypes. Needs a lot of thought.

---

This issue was generated by todo based on a TODO comment in 7651488 when #488 was merged. cc @roblabla.