[export] kill deprecated constraints API (#120860)
Summary:
Previously `export` would take `constraints` built with `dynamic_dim(...)`s. This has been deprecated for a while; one can now pass in a `dynamic_shapes` spec built with `Dim(...)`s.
Here we kill this deprecated API. Eventually this will lead to simplification of the underlying implementation, since the new `Dim`-based specs can map 1-1 with symbolic shapes concepts without going through indirect machinery of `dynamic_dim`-based constraints. It is expected that internal APIs like `_dynamo.export` and `_trace._export_to_torch_ir` will change when that happens.
Leaving `aot_compile` and `capture_pre_autograd_graph` entry points alone for now. This will eventually be updated anyway.
Test Plan: updated tests
Differential Revision: D54339703
Pull Request resolved: https://github.com/pytorch/pytorch/pull/120860
Approved by: https://github.com/suo, https://github.com/tugsbayasgalan
