test_iseq_load: expand tests with stack mismatches

We can ensure the loader works for these cases even if the
reoptimized bytecode is not a match for the original.

* test/-ext-/iseq_load/test_iseq_load.rb
  (test_next_in_block_in_block): test using ISeq#eval
  (test_break_ensure): ditto
  [ruby-core:66988]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@49044 b2dd03c8-39d4-4d8f-98ff-823fe69b080e