Add typetrace(t) for returning the recursive supertypes of Type t

[IanButterworth]

A simple function that might be useful-enough to put in base?
From a discussion with @DilumAluthge and @dpsanders on slack

julia> typetrace(Int32)
"Int32 <: Signed <: Integer <: Real <: Number <: Any"

julia> typetrace(Int32, returnarray=true)
6-element Array{DataType,1}:
 Any    
 Number 
 Real   
 Integer
 Signed 
 Int32  

I can add tests & documentation if there's interest

[IanButterworth]

Perhaps supertypetrace is a better name?

[KristofferC]

Already implemented in #34419?

[IanButterworth]

Ah, damn. Forgot to check master..