Restructuring tests of pipeline, using dune

.github/workflows/proof_tools.yml

proofs/pipeline/examples/Makefile

proofs/pipeline/examples/hello/dune

proofs/pipeline/examples/hello/encoding

proofs/pipeline/examples/hello/hello.expected

proofs/pipeline/examples/hello/hello.log

proofs/pipeline/examples/hello/hello.ml

proofs/pipeline/examples/hello/hello.prf

proofs/pipeline/examples/hello/hello.pvs

proofs/pipeline/examples/hello/lambdapi.pkg

proofs/pipeline/examples/hello/spec/main.lp

proofs/pipeline/examples/run.sh