Add another container for LLVM modules. This one stores one
`llvm::Module` per function (all modules share the same
`llvm::LLVMContext` for performance reasons).
Add the needed infrastructures that allow ephemeral classes (`PipeRun`s)
to be wrapped as a regular pypeline `Pipe` class. These automatically
have their dependencies tracked and propagated to the pypeline.
Giacomo Vercesi