Add map! method with single array param when source and dest are the same

[kim366]

julia> arr = [1,2,3];

julia> map!(x -> 2x, arr)
ERROR: BoundsError: attempt to access ()
  at index [1]
Stacktrace:
 [1] map_n!(::getfield(Main, Symbol("##3#4")), ::Array{Int64,1}, ::Tuple{}) at ./abstractarray.jl:2032
 [2] map!(::getfield(Main, Symbol("##3#4")), ::Array{Int64,1}) at ./abstractarray.jl:2057
 [3] top-level scope at none:0

This code produces a very non-descriptive error and the attempt is clear. Instead, map!(x -> 2x, arr, arr) has to be used, which is not obvious (especially when comparing with map). This PR adds a method to map! that accepts this input and maps in the same array.

[Sacha0]

Ref. #19721. Best!