[llvm] [LLVM][SVE] Improve code generation for vector.insert into posion. (PR #105665)

[Sander de Smalen via llvm-commits]

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

Not sure if I'm the biggest fan of the double-nested `foreach` (expanded it would be 18 patterns, which to my eye would be easier to read) but the changes look correct to me.

https://github.com/llvm/llvm-project/pull/105665