selftests/tc-testing: add selftests for cake_mq qdisc

selftests/tc-testing: add selftests for cake_mq qdisc

Test 684b: Create CAKE_MQ with default setting (4 queues)
Test 7ee8: Create CAKE_MQ with bandwidth limit (4 queues)
Test 1f87: Create CAKE_MQ with rtt time (4 queues)
Test e9cf: Create CAKE_MQ with besteffort flag (4 queues)
Test 7c05: Create CAKE_MQ with diffserv8 flag (4 queues)
Test 5a77: Create CAKE_MQ with diffserv4 flag (4 queues)
Test 8f7a: Create CAKE_MQ with flowblind flag (4 queues)
Test 7ef7: Create CAKE_MQ with dsthost and nat flag (4 queues)
Test 2e4d: Create CAKE_MQ with wash flag (4 queues)
Test b3e6: Create CAKE_MQ with flowblind and no-split-gso flag (4 queues)
Test 62cd: Create CAKE_MQ with dual-srchost and ack-filter flag (4 queues)
Test 0df3: Create CAKE_MQ with dual-dsthost and ack-filter-aggressive flag (4 queues)
Test 9a75: Create CAKE_MQ with memlimit and ptm flag (4 queues)
Test cdef: Create CAKE_MQ with fwmark and atm flag (4 queues)
Test 93dd: Create CAKE_MQ with overhead 0 and mpu (4 queues)
Test 1475: Create CAKE_MQ with conservative and ingress flag (4 queues)
Test 7bf1: Delete CAKE_MQ with conservative and ingress flag (4 queues)
Test ee55: Replace CAKE_MQ with mpu (4 queues)
Test 6df9: Change CAKE_MQ with mpu (4 queues)
Test 67e2: Show CAKE_MQ class (4 queues)
Test 2de4: Change bandwidth of CAKE_MQ (4 queues)
Test 5f62: Fail to create CAKE_MQ with autorate-ingress flag (4 queues)
Test 038e: Fail to change setting of sub-qdisc under CAKE_MQ
Test 7bdc: Fail to replace sub-qdisc under CAKE_MQ
Test 18e0: Fail to install CAKE_MQ on single queue device

Reviewed-by: Victor Nogueira <victor@mojatatu.com>
Signed-off-by: Jonas Köppeler <j.koeppeler@tu-berlin.de>
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Link: https://patch.msgid.link/20260109-mq-cake-sub-qdisc-v8-6-8d613fece5d8@redhat.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>