[Ruby 3.4] Object#singleton_method now returns methods in modules prepended to or included in the receiver's singleton class

[andrykonchin]

Changes:

Object#singleton_method now returns methods in modules prepended to or included in the
receiver's singleton class. [Bug #20620]

o = Object.new
o.extend(Module.new{def a = 1})
o.singleton_method(:a).call #=> 1