selftests: tc: Add generic erspan_opts matching support for tc-flower

Add test cases to tc_flower.sh to validate generic matching on ERSPAN
options. Both ERSPAN Type II and Type III are covered.

Also add check_tc_erspan_support() to verify whether tc supports
erspan_opts.

Signed-off-by: Li Shuang <shuali@redhat.com>
Reviewed-by: Xin Long <lucien.xin@gmail.com>
Link: https://patch.msgid.link/1f354a1afd60f29bbbf02bd60cb52ecfc0b6bd17.1752848172.git.shuali@redhat.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>