bpf/tests: Add exhaustive tests of JMP operand magnitudes

This patch adds a set of tests for conditional JMP and JMP32 operations to
verify correctness for all possible magnitudes of the immediate and
register operands. Mainly intended for JIT testing.
Signed-off-by: Johan Almbladh <johan.almbladh@anyfinetworks.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20210914091842.4186267-6-johan.almbladh@anyfinetworks.com