* Change `import pytensor.tensor as at` to `as pt` everywhere in the docs

* Change `import pytensor.tensor as at` to `as pt` everywhere

Change `import pytensor.scalar as aes` to `as ps` everywhere

Change `import pytensor.tensor.random as aer` to `as ptr` everywhere

Change test variables with `_at` suffix or `at_` prefix to `_pt` and `pt_`, respectively

* More renaming

* Rename remaining instances of `aes` and `aer`