Use an st table for "too complex" objects

	st tables will maintain insertion order so we can marshal dump / load
	objects with instance variables in the same order they were set on that
	particular instance

	[ruby-core:112926] [Bug #19535]

Co-Authored-By: Jemma Issroff <jemmaissroff@gmail.com>
	---
	 gc.c                     | 10 ++++------
	 include/ruby/st.h        |  2 ++
	 object.c                 |  2 +-
	 ractor.c                 | 43 ++++++++++++++++++++++---------------------
	 shape.h                  |  6 +++---
	 st.c                     |  6 ++++++
	 test/ruby/test_shapes.rb | 21 +++++++++++++++++++++
	 variable.c               | 28 ++++++++++++++--------------
	 vm_insnhelper.c          |  2 +-
	 9 files changed, 74 insertions(+), 46 deletions(-)