Fix AliasAnalysisKind::PURE on MSVC (#25375)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/25375
Either MSVC or the Windows headers have a PURE macro defined and will replace
any occurrences of the PURE token in code with an empty string. Replace
AliasAnalysisKind::PURE with AliasAnalysisKind::PURE_FUNCTION.
Note: this is bc breaking.
ghstack-source-id: 89202222
Test Plan: unit tests
Differential Revision: D17107743
fbshipit-source-id: 899a20651ba32d50691956b5424b351586c21cec
