bpf: Add unit tests for bpf_line_info

Add unit tests for bpf_line_info for both BPF_PROG_LOAD and
BPF_OBJ_GET_INFO_BY_FD.

jit enabled:
[root@arch-fb-vm1 bpf]# ./test_btf -k 0
BTF prog info raw test[5] (line_info (No subprog)): OK
BTF prog info raw test[6] (line_info (No subprog. insn_off >= prog->len)): OK
BTF prog info raw test[7] (line_info (No subprog. zero tailing line_info): OK
BTF prog info raw test[8] (line_info (No subprog. nonzero tailing line_info)): OK
BTF prog info raw test[9] (line_info (subprog)): OK
BTF prog info raw test[10] (line_info (subprog + func_info)): OK
BTF prog info raw test[11] (line_info (subprog. missing 1st func line info)): OK
BTF prog info raw test[12] (line_info (subprog. missing 2nd func line info)): OK
BTF prog info raw test[13] (line_info (subprog. unordered insn offset)): OK

jit disabled:
BTF prog info raw test[5] (line_info (No subprog)): not jited. skipping jited_line_info check. OK
BTF prog info raw test[6] (line_info (No subprog. insn_off >= prog->len)): OK
BTF prog info raw test[7] (line_info (No subprog. zero tailing line_info): not jited. skipping jited_line_info check. OK
BTF prog info raw test[8] (line_info (No subprog. nonzero tailing line_info)): OK
BTF prog info raw test[9] (line_info (subprog)): not jited. skipping jited_line_info check. OK
BTF prog info raw test[10] (line_info (subprog + func_info)): not jited. skipping jited_line_info check. OK
BTF prog info raw test[11] (line_info (subprog. missing 1st func line info)): OK
BTF prog info raw test[12] (line_info (subprog. missing 2nd func line info)): OK
BTF prog info raw test[13] (line_info (subprog. unordered insn offset)): OK

Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Acked-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>