Parse symbolic shapes (#69775)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/69775
Adds parsing for Symbolic Shapes.
Test Plan: Imported from OSS
Reviewed By: jbschlosser
Differential Revision: D33515233
Pulled By: eellison
fbshipit-source-id: 7ebb22c0ab37d78e459ebcab67bb86f731d00376
