Unify and simplify the FastCloneShallowArrayStub

- Don't bake in length/capacity into full codegen calls of stubs,
  allowing boilerplates to increase their capacity without regenerating
  code.
- Unify all variants of the clone stub into a single,
  length-independent version.
- Various tweaks to make sure that the clone stub doesn't spill and
  therefore need an eager stack frame.
- Handle all lengths of array literals in the fast case.

R=mvstanton@chromium.org

Review URL: https://codereview.chromium.org/257563004

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@20974 ce2b1a6d-e550-0410-aec6-3dcde31c8c00