This PR neither adds nor removes material, but improves the organization
of `Init/Data/List/*`.
These files are essentially completely re-ordered, to ensure that
material is developed in a consistent order between `List.Basic`,
`List.Impl`, `List.BasicAux`, and `List.Lemmas`.
Everything is organised in subsections, and I've added some module docs.
In the following, hovering over `true` in the infoview was showing
`Nat.succ y`.
```lean
#check fun (x : Nat) =>
match h : x with
| 0 => false
| y + 1 => true
```
Now hovering over `true` shows `true`.
The issue was that SubExpr positions were not being tracked for
patterns, and the position for a pattern could coincide with the
position for a RHS, putting overwriting terminfo. Now the position given
to a pattern is correct and unique.
Refactors the `match` delaborator, makes it handle shadowing of `h :`
discriminant annotations correctly, and makes it use the standard
`withOverApp` combinator to handle overapplication.
