4. Factor out the unit-norm basis (and operator symmetry) tests once
all of the algebras pass.
-5. Override inner_product(), _max_test_case_size(), et cetera in
- DirectSumEJA.
+5. Override random_instance(), one(), et cetera in DirectSumEJA.
6. Switch to QQ in *all* algebras for _charpoly_coefficients().
This only works when we know that the basis can be rationalized...