Deprecate `pytensor.tensor.math._tensordot_as_dot` and the methods that use it

[lucianopaz]

Description

While working on #606 and #607 it became apparent that pytensor.tensor.math._tensordot_as_dot is hard to read or understand, and that it was defective. In #607 we opted to port the implementation from numpy directly into pytensor making _tensordot_as_dot practically useless. The only functions that still use it are batched_dot (indirectly) and batched_tensordot. I think that both of these could be deprecated or at least re-written to use Blockwise.