[IR] Removed IRScope references from Break and NonlocalReturn instrs.

* All IRScopes add two pieces of IR information to the static scopes
  that are created: (a) scope-type (b) scope-id. These two bits are
  sufficient to support breaks and non-local returns.

* This eliminates all IRScope references and uses from IRRuntimeHelpers
  as well.

* This should now make it easier for the JIT to support them.