[BUG] Improve python tests of ANN algorithm for `int8`/`uint8` and `inner_product`

[lowener]

ANN algorithm with metric=inner_product and dtype=int8 or uint8 are not tested properly. In pytest the dataset generated is in (u)int8, then it gets normalized and transformed in float. So when testing those dtypes the pytests are skipped (cagra) or they end up testing float inputs (ivf_flat/pq).

The inner_product is compared with sklearn cosine since they don't have IP distance, but the queries are also not normalized.