feat: support for fold/unfold (#1735)

* refactor: add Ops.convolution and make NNlib call that

* feat: support unfold

* fix: don't emit large constants

* feat: support fold

* ci: use 1.11

* test: use <=3.14 for now

* test: add tests from nnlib

* chore: run fmt

* fix: materialize

Author: avik-pal