tc-testing: Split test case files into smaller chunks

The original submission had the test cases stored in one
monolithic file. This can be unwieldy to edit, especially as more
test cases are added. This patch removes the original tests.json
file in favour of individual ones broken down by category.

Signed-off-by: Lucas Bates <lucasb@mojatatu.com>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>