Fix no-arg ScopedValues.@with within a scope (#56019)

Fixes #56017

(cherry picked from commit 57e3c9e)

Author: IanButterworth

base/scopedvalues.jl

@@ -85,6 +85,8 @@ struct Scope
     values::ScopeStorage
 end
 
+Scope(scope::Scope) = scope
+
 function Scope(parent::Union{Nothing, Scope}, key::ScopedValue{T}, value) where T
     val = convert(T, value)
     if parent === nothing

test/scopedvalues.jl

@@ -135,6 +135,12 @@ end
         @test sval[] == 1
         @test sval_float[] == 1.0
     end
+    @with sval=>2 sval_float=>2.0 begin
+        @with begin
+            @test sval[] == 2
+            @test sval_float[] == 2.0
+        end
+    end
 end
 
 @testset "isassigned" begin