[llvm] [VectorCombine] Added pattern for recognising the construction of packed integers. (PR #147414)

[Simon Pilgrim via llvm-commits]

https://github.com/RKSimon commented:

Its recommended that only cost based vector folds use VectorCombine - general vector simplifications/canonicalizations should use InstCombine. 

https://github.com/llvm/llvm-project/pull/147414