This is probably too big for one commit...

The main goal here is to hack the dtb instructions into execution to
match Spike. Since these instructions don't exist in the ELF, they are
manually stored to and loaded from the memory module.

Program instructions were previously loaded from the ELF module itself,
rather than from memory. These have been moved to memory so we aren't
trying to fetch instructions from two different places. This lead to
some other refactoring that might've been outside of the scope of this
commit but were necessary to minimize a likeness to spaghetti.

* Vemu is now encapsulated in its own package with a Builder
* The load pacakge is much smaller and can be used elsewhere