Merge branch 'Parallelize verif_scale selftests'

Andrii Nakryiko says:

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Reduce amount of waiting time when running test_progs in parallel mode (-j) by
splitting bpf_verif_scale selftests into multiple tests. Previously it was
structured as a test with multiple subtests, but subtests are not easily
parallelizable with test_progs' infra. Also in practice each scale subtest is
really an independent test with nothing shared across all substest.

This patch set changes how test_progs test discovery works. Now it is possible
to define multiple tests within a single source code file. One of the patches
also marks tc_redirect selftests as serial, because it's extremely harmful to
the test system when run in parallel mode.
====================

Acked-by: Yucong Sun <sunyucong@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>