Streamline Build System

[ericthewry]

Migrate build system from a mishmash of opam, dune, and coq makefiles to just dune. The goal is to allow incremental builds to reduce iteration time, instead of requiring a full (20 minute) rebuild of poulet4 and poulet4_Ccomp.

I'm not a dune expert, so please kick the tires and figure out what's not working or can be made more ergonomic

Changes

• poulet4_Ccomp is now build using dune. The extraction is also managed using dune which means that Extract.v moved from lib to extraction, and the extraction/dune file contains all of the required files.
• poulet4 and poulet4_Ccomp are no longer pinned when building petr4
• *.opam files are generated from dune-project

[ericthewry]

@rhd @pataei The build is fixed now. please have a look!

[hackedy]

Works for me. Had to run git clean -fdx in the deps/poulet4_Ccomp/extraction directory to clear out some stale state from the old build system first.