Add random graph generation (#188)

* Add pytato.squeeze

* add test

* use are_shape_components_equal

Co-authored-by: Kaushik Kulkarni <15399010+kaushikcfd@users.noreply.github.com>

* fix

* Add random graph generation

* push current state

* Random DAG generator actually tests things

* Fix show_dot_graph invocation that tripped up pylint

* DataInterface: document dtype, shape as read-only

* Type-annotate, type-check testlib

* Style/name/comment fixes from Kaushik's review

Co-authored-by: [6~ <inform@tiker.net>
Co-authored-by: Kaushik Kulkarni <15399010+kaushikcfd@users.noreply.github.com>