Always show "closest candidates" when there is a MethodError

[nickrobinson251]

Currently we have heuristics for building a list of "closest candidate" methods to display when a user hits a MethodError, but these heuristics can result in no methods making the list... so we show none of the valid methods which seems less helpful than showing some (/any) of the valid methods.

For example, this seems to happens if none of the argument types match and more than two arguments were given.

julia> foo(x::Int, y::Int, z=1, a=2) = 1;

julia> foo("a")  
ERROR: MethodError: no method matching foo(::String)
Closest candidates are:
  foo(::Int64, ::Int64) at REPL[1]:1
  foo(::Int64, ::Int64, ::Any) at REPL[1]:1
  foo(::Int64, ::Int64, ::Any, ::Any) at REPL[1]:1
Stacktrace:
 [1] top-level scope
   @ REPL[2]:1

julia> foo("a", "b")  # why no "Closest candidates"?
ERROR: MethodError: no method matching foo(::String, ::String)
Stacktrace:
 [1] top-level scope
   @ REPL[3]:1

julia/base/errorshow.jl

Line 484 in 35ac6e1

if right_matches > 0 || length(arg_types_param) < 2

I don't know why this heuristic was chosen, and I think we should remove such heuristics that discard methods. We can still show only 3 candidates and ordered by some measure of "closeness", but showing some methods seems strictly more informative than showing none.

very related to #32470 (but i've opened this separately as this is a more narrow request and that one seem to have become about how to print this information in a good way, rather than which methods to print)