Stack from ghstack:

• [WIP] Add CI job to check function schemas' backward compatiblity #23422 [WIP] Add CI job to check function schemas' backward compatiblity
• Add isBackwardCompatibleWith for Argument and FunctionSchema #23409 Add isBackwardCompatibleWith for Argument and FunctionSchema
• expose parse_schema and __eq__ function to python and add round trip tests #23208 expose parse_schema and eq function to python and add round trip tests
• Expose an API to iterate all the registered operators #23207 Expose an API to iterate all the registered operators
• Align AliasInfo's operator<< with FunctionSchema #23206 Align AliasInfo's operator<< with FunctionSchema
• Support IntList in Dict's shalloEquals #23205 Support IntList in Dict's shalloEquals
• Support variadic returns in Schema's operator<< #23204 Support variadic returns in Schema's operator<<

Required when comparing IntList type of default values

Differential Revision: D16433809