FILTERS: Fixed 2nd order raw scalar issue

There was a mix-up when shifting the history in the scalar code path.

Signed-off-by: Gama <misept.dieseneuf@gmail.com>
TESTS: Minor changes to debug utilities

- All debug stuff now lies in its own namespace.
- No longer ambiguous overload for "Push" when using scalar code path.

Signed-off-by: Gama <misept.dieseneuf@gmail.com>