make test: split into basic and extended tests

make test: split into basic and extended tests

Implement plumbing to allow decorating tests as extended, e.g.:

@unittest.skipUnless(running_extended_tests(), "part of extended tests")

both methods and classes can be decorated this way.

Change make test and make test-debug to run only non-extended tests.
Introduce make test-all and make test-all-debug to run the full suite.
Run full suite as part of make verify.
Decorate most BFD tests as extended.

Change-Id: I3bc64f59e9fe238f7f767d7e043dc165d03e9dfa
Signed-off-by: Klement Sekera <ksekera@cisco.com>