Implements the pretty printer option `pp.numericTypes` for including a
type ascription for numeric literals. For example, `(2 : Nat)`, `(-2 :
Int)`, and `(-2 / 3 : Rat)`. This is useful for debugging how arithmetic
expressions have elaborated or have been otherwise transformed. For
example, with exponentiation is is helpful knowing whether it is `x ^ (2
: Nat)` or `x ^ (2 : Real)`. This is like the Lean 3 option
`pp.numeralTypes` but it has a wider notion of a numeric literal.
Also implements the pretty printer option `pp.natLit` for including the
`nat_lit` prefix for raw natural number literals.
Closes#3021
