YALO warnings trigger on ppx generated code

[NathanReb]

See this warning (and multiple similar others) that are reported by yalo on oui's test suite:

File "tests/oui_lib/test_string_with_vars.ml", lines 37-41, characters 0-87
Warning (YALO+10): Inner module "Ppx_expect_test_block" should be fully uppercase ("PPX_EXPECT_TEST_BLOCK" here)

00035     [%expect {| { String_with_vars.subst_string = "<x>.<y>"; unknown_vars = ["<x>"; "<y>"] } |}]
00036
00037 > let%expect_test "subst: unknown var reported once" =
00038 >   let t = of_string "<x>.<x>" in
00039 >   let res = subst ~install_path:"XX" t in
00040 >   Format.printf "%a" pp_subst_result res;
00041 >   [%expect {| { String_with_vars.subst_string = "<x>.<x>"; unknown_vars = ["<x>"] } |}]
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
00042

It appears this triggers from inside the ppx-generated code which is something we probably don't want for a large variety of warnings.

There are a few ways to approach this such as running on non preprocessed sources or not running linters on ghost loc AST nodes (which won't always work as not all ppx-es will generate nodes with ghost locations).

Note that this can probably occur with other warnings as well!