selftests/tc-testing: add selftests for fq_codel qdisc

Test 4957: Create FQ_CODEL with default setting
Test 7621: Create FQ_CODEL with limit setting
Test 6871: Create FQ_CODEL with memory_limit setting
Test 5636: Create FQ_CODEL with target setting
Test 630a: Create FQ_CODEL with interval setting
Test 4324: Create FQ_CODEL with quantum setting
Test b190: Create FQ_CODEL with noecn flag
Test 5381: Create FQ_CODEL with ce_threshold setting
Test c9d2: Create FQ_CODEL with drop_batch setting
Test 523b: Create FQ_CODEL with multiple setting
Test 9283: Replace FQ_CODEL with noecn setting
Test 3459: Change FQ_CODEL with limit setting
Test 0128: Delete FQ_CODEL with handle
Test 0435: Show FQ_CODEL class
Signed-off-by: Zhengchao Shao <shaozhengchao@huawei.com>
Reviewed-by: Victor Nogueira <victor@mojatatu.com>
Tested-by: Victor Nogueira <victor@mojatatu.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>