bpf/tests: Add staggered JMP and JMP32 tests

This patch adds a new type of jump test where the program jumps forwards
and backwards with increasing offset. It mainly tests JITs where a
relative jump may generate different JITed code depending on the offset
size, read MIPS.
Signed-off-by: Johan Almbladh <johan.almbladh@anyfinetworks.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20210914091842.4186267-7-johan.almbladh@anyfinetworks.com