A ws server vhost and an RFC 8441 h2 ws client in one process.  The
server bulk-sends a 64KB pattern in 1KB lws_write() chunks gated only
on lws_send_pipe_choked(), like typical user code; the client connects
with LCCSCF_H2_MANUAL_RXFLOW and drip-feeds tx credit in 1KB
WINDOW_UPDATE quanta, forcing the h2 role to park DATA and split
frames to fit the window.

Fails (within a second) if the connection doesn't come up as genuine
ws-over-h2, if the client ever receives more ws payload than it has
granted credit for -- only possible when the server ignored the peer's
window -- or if the pattern is corrupted / incomplete; passes when the
whole transfer arrives in-window.  Wired into ctest like the other
api-tests.