fix(lint): consolidate test runners, fix .mli exports, rename psl_test (E410, E600, E618, E620)

- requests: convert test_signature, test_websocket, test_rfc9421_vectors
to modules exporting suite; add test.ml runner; delete standalone .mli
for test_simple/test_simple_head
- punycode: consolidate 2 test stanzas into single test.ml runner;
add .mli files; fix ace_prefix doc (E410)
- publicsuffix: rename psl_test.ml → test_psl.ml (E618)
- rpmsg: add missing test_rpmsg.mli and test_wire.mli (E600)