Move test of stackoverflow with close(::Channel) to stack_overflow.jl (#49702)

Per @vtjnash's comment here:
https://github.com/JuliaLang/julia/pull/49508/files/bca5ac79d04fb2a95f3b9a7b7448fe5b478f950b#r1186161259

> the handling of this error is quite bad and sometimes ends up breaking
> the process (as I found out today trying to debug something completely
> unrelated)

This is a Tests-only PR

Author: NHDaly

test/channels.jl

@@ -626,20 +626,3 @@ end
         @test n_avail(c) == 0
     end
 end
-
-# Issue #49507: stackoverflow in type inference caused by close(::Channel, ::Exception)
-@testset "close(::Channel, ::StackOverflowError)" begin
-    ch = let result = Channel()
-        foo() = try
-            foo()
-        catch e;
-            close(result, e)
-        end
-
-        foo()  # This shouldn't fail with an internal stackoverflow error in inference.
-
-        result
-    end
-
-    @test (try take!(ch) catch e; e; end) isa StackOverflowError
-end

test/stack_overflow.jl

@@ -17,3 +17,20 @@ let exename = Base.julia_cmd()
     @show readchomperrors(`$exename -e "f() = f(); f()"`)
     @show readchomperrors(`$exename -e "f() = f(); fetch(@async f())"`)
 end
+
+# Issue #49507: stackoverflow in type inference caused by close(::Channel, ::Exception)
+@testset "close(::Channel, ::StackOverflowError)" begin
+    ch = let result = Channel()
+        foo() = try
+            foo()
+        catch e;
+            close(result, e)
+        end
+
+        foo()  # This shouldn't fail with an internal stackoverflow error in inference.
+
+        result
+    end
+
+    @test (try take!(ch) catch e; e; end) isa StackOverflowError
+end