[IR] Some more fixes and FIXMEs to inlining code

* More progress inlining code on bench_method_dispatch.rb

* The next set of crashers in inlining requires fixes to the
  WrappedIRClosure operand to take an explicit self arg so that
  on inlining, the correct (original) self can be passed into
  the block rather than passing the self from the host scope
  into which code got inlined. TO BE DONE.