bpf/tests: Add exhaustive tests of ALU register combinations

This patch replaces the current register combination test with new
exhaustive tests. Before, only a subset of register combinations was
tested for ALU64 DIV. Now, all combinatons of operand registers are
tested, including the case when they are the same, and for all ALU32
and ALU64 operations.

Signed-off-by: Johan Almbladh <johan.almbladh@anyfinetworks.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20211001130348.3670534-8-johan.almbladh@anyfinetworks.com