The control-flow graph and all its hierarchy components
have been moved from `model` to `efa`. The CFG is now
serialized onto the LLVM IR module as a metadata.
The collection of the function entry-points has now been separated
from EarlyFunctionAnalysis into two distinct passes: the first one,
which collects functions which are in call-sites of a direct call,
and the second one which collects code pointers in `.rodata` (e.g.,
function pointers, vtables; jump-tables are possibly skipped).