[llvm] [LLVM][DAGCombiner] Extend coverage for insert_subv(undef, extract_subv(A, 0), 0) (PR #95242)

[David Sherwood via llvm-commits]

https://github.com/david-arm approved this pull request.

LGTM! Some improved codegen for the SVE streaming mode tests. :)

https://github.com/llvm/llvm-project/pull/95242