Drop support of uncompressing zstd-compressed modules in `revng opt` as
this functionality has been moved within `llvm`.
(This is a revert of commit dd8d158e47)
Package revng's python code in two wheels: `revng` and `revng_internal`.
The revng wheel contains the
`revng.{pipeline_description,model,tupletree}` modules, while the
`revng_internal` one everything under `revng.internal`.