selftests/tc-testing: add selftests for hhf qdisc

Test 4812: Create HHF with default setting
Test 8a92: Create HHF with limit setting
Test 3491: Create HHF with quantum setting
Test ba04: Create HHF with reset_timeout setting
Test 4238: Create HHF with admit_bytes setting
Test 839f: Create HHF with evict_timeout setting
Test a044: Create HHF with non_hh_weight setting
Test 32f9: Change HHF with limit setting
Test 385e: Show HHF class

Signed-off-by: Zhengchao Shao <shaozhengchao@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>