refactor(crowbar): Alcotest-style API with suite exports and grouped run
- Change `run` signature to `string -> (string * test_case list) list -> unit`
matching Alcotest's grouping convention
- Fix `_name` bug: pass the name through to Alcotest.run_with_args
- Each fuzz module now exports `let suite = ("name", [test_case ...])`
- Entry points (fuzz.ml) collect suites: `Crowbar.run "pkg" [Fuzz_X.suite]`
- Remove stale `add_test`/`suite` API, keep only `test_case`/`run`
- Remove `let run () = ()` from fuzz_common.ml files
- Update merlint E725 rule to match new `let suite = ("name", ...)` pattern
- Update E725 test fixtures and expected output