bpf/tests: Add JMP tests with degenerate conditional

This patch adds a set of tests for JMP and JMP32 operations where the
branch decision is know at JIT time. Mainly testing JIT behaviour.

Signed-off-by: Johan Almbladh <johan.almbladh@anyfinetworks.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20210914091842.4186267-11-johan.almbladh@anyfinetworks.com