selftests/bpf: Add verifier tests for code pattern '<const> <cond_op> <non_const>'

Add various tests for code pattern '<const> <cond_op> <non_const>' to
exercise the previous verifier patch.

The following are veristat changed number of processed insns stat
comparing the previous patch vs. this patch:

File                                                   Program                                               Insns (A)  Insns (B)  Insns  (DIFF)
-----------------------------------------------------  ----------------------------------------------------  ---------  ---------  -------------
test_seg6_loop.bpf.linked3.o                           __add_egr_x                                               12423      12314  -109 (-0.88%)

Only one program is affected with minor change.
Signed-off-by: Yonghong Song <yhs@fb.com>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20230406164510.1047757-1-yhs@fb.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>