Drop using the `revng-` prefix from all executables under
`libexec/revng/`. Now any executable found under there that is
executable and without extension will be considered a `revng`
subcommand, following the usual command-line rules.
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`.