Clear-up all calls to packSCMP

[jcp19]

For now, I can provide an ideal spec, which can later be confirmed by the PR from @Dspil

TODO:

• come up with ideal spec for packSCMP and verify the entire codebase accordingly @jcp19
• verify packSCMP with the contract up until the call to prepareSCMP @jcp19
• verify the remainder of prepareSCMP such that packSCMP verifies @Dspil

[jcp19]

Note to self:
The ideal spec should take full perms for the ub, should return most of it (1 - R15) as well as a wand from the R15 address if it aliases to R15 of the ub, otherwise should give the ub (R15) already. It should also satisfy p.d.validResult. I will take care of this after all open tasks in #240 are handled