test/recv-mshot-fair: test fairness and limits between streams

Based on code slated for 6.17, test that multiple streams don't end
up starving each other, if limited by setting sqe->len on recv
multishot.

Also test that if sqe->optlen is set for a recv multishot, then
the multishot request should terminate when this limit is hit.

Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: axboe

test/Makefile

@@ -180,6 +180,7 @@ test_srcs := \
 	recv-inc-ooo.c \
 	recv-msgall.c \
 	recv-msgall-stream.c \
+	recv-mshot-fair.c \
 	recv-multishot.c \
 	reg-fd-only.c \
 	reg-hint.c \