Bender.yml: Move generated include dir into source group

[fischeti]

Fixes a bender warning for non-existent include dirs. In my opinion hw/generated should not be a exported include dir, since snitch_cluster_wrapper is either generated in snitch_cluster itself behind a target (where I also added the include dir now), or it is generated externally (see picobello), where the include dirs anyway have to be specified manually.

[colluca]

Actually, it seems I rushed a bit too much with this one (should've gone through develop).

Compilation with QuestaSim breaks. Works with Verilator for some reason, which is why it wasn't catched in the Github CI.

The problem is that include_dirs is tied to the file group in which it is specified, not to the target (e.g. snitch_cluster_wrapper). And snitch_cluster_wrapper.sv is not the only generated file in hw/generated, snitch_cluster_addrmap.svh is too, which is giving error. So include_dirs has to be added to all file groups in which at least one file includes something from hw/generated.

As a matter of fact, now that I come to think about it better, I don't even think we need the include_dirs in the group containing snitch_cluster_wrapper.sv, since this file doesn't include anything.

I'm temporarily reverting this change, but we can readdress this in a separate PR.