don't taint :terminates because of the loop in afoldl (#57353)

The iteration count is always finite.

Author: nsajko

base/operators.jl

@@ -593,6 +593,7 @@ const ⊽ = nor
 # method count limit in inference
 afoldl(op, a) = a
 function afoldl(op, a, bs...)
+    @_terminates_locally_meta
     l = length(bs)
     i =  0; y = a;            l == i && return y
     #@nexprs 31 i -> (y = op(y, bs[i]); l == i && return y)

test/operators.jl

@@ -350,6 +350,7 @@ end
 end
 
 @test [Base.afoldl(+, 1:i...) for i = 1:40] == [i * (i + 1) ÷ 2 for i = 1:40]
+@test Core.Compiler.is_terminates(Base.infer_effects(Base.afoldl, Tuple{typeof(+), Vararg{Int, 100}}))
 
 @testset "Returns" begin
     @test @inferred(Returns(1)()   ) === 1