[llvm] [DAG] SDPatternMatch - Add m_ExtractElt and m_InsertElt matchers (PR #119430)

[Chris White via llvm-commits]

whiteio wrote:

Hey @RKSimon, could you have a look at this when you have the time please? I don't have permissions to add reviewers

https://github.com/llvm/llvm-project/pull/119430