enum.rb: fix Array#hash infinite loop with self-referencing enumerables

Modify `Enumerable#hash` to use `__method_recursive?(:hash)` for recursion
detection, preventing infinite loops when hashing self-referencing enumerables.
Add a test case to verify the fix.

Co-authored-by: Gemini <gemini@google.com>

test/t/array.rb

@@ -468,3 +468,11 @@ assert('Array#delete') do
   assert_equal nil, a.delete(nil) { "?" }
   assert_equal [], a
 end
+
+assert('Array#hash with self-referencing arrays') do
+  a = []
+  a << a
+  b = []
+  b << b
+  assert_equal a.hash, b.hash
+end