tools: ynl: convert tc and tc-filter-add samples to selftest

tools: ynl: convert tc and tc-filter-add samples to selftest

Convert tc.c and tc-filter-add.c to produce KTAP output with
kselftest_harness. Merge the two tests together. They both
test TC one is testing qdisc and the other classifiers but
they can easily live in a single selftest.

Make the test spawn a new netns, and run the operations on
lo to avoid onerous setup and cleanup.

  TAP version 13
  1..2
  # Starting 2 tests from 1 test cases.
  #  RUN           tc.qdisc ...
  #               lo: fq_codel  limit: 10240p target: 5ms new_flow_cnt: 0
  #            OK  tc.qdisc
  ok 1 tc.qdisc
  #  RUN           tc.flower ...
  # flower pref 1 proto: 0x8100
  # flower:
  #   vlan_id: 100
  #   vlan_prio: 5
  #   num_of_vlans: 3
  # action order: 1 vlan push id 200 protocol 0x8100 priority 0
  # action order: 2 vlan push id 300 protocol 0x8100 priority 0
  #            OK  tc.flower
  ok 2 tc.flower
  # PASSED: 2 / 2 tests passed.
  # Totals: pass:2 fail:0 xfail:0 xpass:0 skip:0 error:0

Reviewed-by: Donald Hunter <donald.hunter@gmail.com>
Tested-by: Donald Hunter <donald.hunter@gmail.com>
Link: https://patch.msgid.link/20260307033630.1396085-6-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>