Opam test suite

There is 3 different kind of tests

• CRAM test in reftests. It is used to check opam behaviour. See reftests/readme.md for more details.
• Bench tests in bench, using current-bench. It is used to benchmark some specific operations.
• OCaml tests in lib. For the moment it is used to check some type manipulation and patch code.

There is also other tests:

• opam-rt: historical test suite. it is a mix of opam cli calls and library usage. It is meant to be removed once all test has been ported to reftests and lib
• opam-crowbar: some fuzz testing of some opam library main types.