merge revision(s) ebb96fa8808317ad53a4977bff26cf755d68077e: [Backport #17321]

	Fix singleton class cloning

	Before this commit, `clone` gave different results depending on whether the original object
	had an attached singleton class or not.

	Consider the following setup:
	```
	class Foo; end
	Foo.singleton_class.define_method(:foo) {}

	obj = Foo.new

	obj.singleton_class if $call_singleton

	clone = obj.clone
	```

	When `$call_singleton = false`, neither `obj.singleton_class.singleton_class` nor
	`clone.singleton_class.singleton_class` own any methods.

	However, when `$call_singleton = true`, `clone.singleton_class.singleton_class` would own a copy of
	`foo` from `Foo.singleton_class`, even though `obj.singleton_class.singleton_class` does not.

	The latter case is unexpected and results in a visibly different clone, depending on if the original object
	had an attached class or not.

	Co-authored-by: Ufuk Kayserilioglu <ufuk.kayserilioglu@shopify.com>
	---
	 class.c                 | 31 ++++++++++++++++++++++---------
	 test/ruby/test_class.rb | 47 +++++++++++++++++++++++++++++++++++++++++++++++
	 2 files changed, 69 insertions(+), 9 deletions(-)

1 files changed, 1 insertions, 1 deletions

diff --git a/version.h b/version.h
index b5c6533881..c0e2f3f081 100644
--- a/version.h
+++ b/version.h
@@ -2,7 +2,7 @@
 # define RUBY_VERSION_MINOR RUBY_API_VERSION_MINOR
 #define RUBY_VERSION_TEENY 3
 #define RUBY_RELEASE_DATE RUBY_RELEASE_YEAR_STR"-"RUBY_RELEASE_MONTH_STR"-"RUBY_RELEASE_DAY_STR
-#define RUBY_PATCHLEVEL 168
+#define RUBY_PATCHLEVEL 169
 
 #define RUBY_RELEASE_YEAR 2021
 #define RUBY_RELEASE_MONTH 3