Informative error in promotion with conflicting promote_rules

[jishnub]

This is the non-controversial change from #56779 that improves the error message in type promotion.

On master, promotion with conflicting promote_rule definitions leads to a stack overflow:

julia> struct PromoteB end

julia> struct PromoteA end

julia> Base.promote_rule(::Type{PromoteA}, ::Type{PromoteB}) = PromoteA

julia> Base.promote_rule(::Type{PromoteB}, ::Type{PromoteA}) = PromoteB

julia> promote_type(PromoteA, PromoteB)
Warning: detected a stack overflow; program state may be corrupted, so further execution might be unreliable.
ERROR: StackOverflowError:
Stacktrace:
      [1] promote_result(::Type, ::Type, ::Type{PromoteA}, ::Type{PromoteB})
        @ Base ./promotion.jl:337
      [2] promote_type
        @ ./promotion.jl:317 [inlined]--- the above 2 lines are repeated 79982 more times ---

In this PR, this is changed to an ArgumentError:

julia> promote_type(PromoteA, PromoteB)
ERROR: ArgumentError: promote_type(PromoteA, PromoteB) failed, as conflicting promote_rule definitions were detected with both PromoteA and PromoteB being possible results.

[nsajko]

s/imformative/informative, for the title.

I think this fixes #13193? EDIT: it doesn't

[nsajko]

I think these methods are not necessary

Suggested change

	promote_result(::Type,::Type,::Type{T},::Type{T}) where {T} = T
	# If only one promote_rule is defined, use the definition directly
	promote_result(::Type,::Type,::Type{T},::Type{Bottom}) where {T} = T
	promote_result(::Type,::Type,::Type{Bottom},::Type{T}) where {T} = T

[nsajko]

more comprehensive PR: #57517

I reduced the scope of that PR, so now it doesn't strictly encompass this PR. However, if my PR gets merged, this PR will not be a bugfix PR any more, seeing as my PR will already prevent a stack overflow. It might still make sense to merge both for the better error messages.