* Virtualize some things that crash when layout descriptor is missing

* More shape specialization

* (very bare) skeleton for dyn elimination

* Miscellaneous

* Lift i32->int64-only restriction on constant folding for Convert

* Add constant folding for ShapeOf, and some tests for new constant folders

* Tests for DynElimination

* Rename specialize_shapes to specialize_function, and add a unit test for value substitution

* Roll back overeager API change in dyn slice bprop (it has to handle right-indexed axes; bummer)

* Add a test for dynamic usage of transpose op

* Fix warning/error about variable shadowing

* Strengthen checks in apply_permutation

* Propagate Constant shapes through Transpose

* Add CHANGE_DYNAMIC_STATE where appropriate

* PR feedback, and fix unit test failure

* Fix PR reference in comment

* PR comments

* Comments for helper funcs

* Remove unique_ptr indirection for the AlignedBuffers

* Fix incorrect indexing of AlignedBuffer vector (whoops\!)

* Remove unnecessary CHANGE_DYAMIC_STATEs

* De-update pass property unit test for const folding

* Replace mystery runes with all_pass_property_off