effects: add reflection utility for the new effect analysis

[aviatesk]

This commit adds new reflection utility named Base.infer_effects that
works in the same way as Base.return_types but returns inferred effects
instead. It would be helpful to test that certain method call has an
expected effects.

For example, we can now remove Base.@pure annotation from the definition of
BroadcastStyle(a::A, b::B) where {A<:AbstractArrayStyle{M},B<:AbstractArrayStyle{N}} where {M,N}
and checks it's still eligible for concrete evaluation like this
(see #44776 (comment) for the context):

julia> import Base.Broadcast: AbstractArrayStyle, DefaultArrayStyle, Unknown

julia> function BroadcastStyle(a::A, b::B) where {A<:AbstractArrayStyle{M},B<:AbstractArrayStyle{N}} where {M,N}
           if Base.typename(A) === Base.typename(B)
               return A(Val(max(M, N)))
           end
           return Unknown()
       end
BroadcastStyle (generic function with 1 method)

julia> # test that the above definition is eligible for concrete evaluation
       @test Base.infer_effects(BroadcastStyle, (DefaultArrayStyle{1},DefaultArrayStyle{2},)) |> Core.Compiler.is_total_or_error
Test Passed

[aviatesk]

I'd like to merge #44786 first before merging this PR.

[aviatesk]

Note: I will add Core.Compiler.return_type alternative for this in this PR (or in another PR). It will come with tfunc and similar supports so that we can fold inferred effects at compile time when possible (albeit it can be unreliable as return_type).

[aviatesk]

Ok, I'd like to move this forward quickly if possible, and let me work on Core.Compiler.infer_effects in another PR. @tkf can I ask your review on this?

[aviatesk]

I think it's not too clear what effects we should return for this case.
For now, I made the result equivalent to the following case:

julia> function f_no_methods end
f_no_methods (generic function with 0 methods)

julia> Base.infer_effects() do
           throw(MethodError(f_no_methods, ()))
       end
(+c,+e,?n,+t)

[tkf]

I can't review all the details but it LGTM! The API is what I wanted.