Deprecate symmetric_axes and use symmetries (arbitrary groups) for all FLOP counting

[wiwu2390]

Currently, the public API for SymmetricTensor only includes symmetric_axes, which is confusing because we also have support for arbitrary permutation groups.

I think we should:

1. Deprecate symmetric_axes
2. Unify the nomenclature around symmetries/groups/symmetry_groups, which I think are all the same thing
3. Allow passing partitions of indices to symmetries, which are automatically cast to the corresponding Young group. (I.e., this should match the old behavior of symmetric_axes)
4. Make sure symmetries and not symmetric_axes is used for all FLOP counting