[polly] [Polly] Allocate packed arrays of matrix multiplication on heap (PR #226163)

[Michael Kruse via llvm-commits]

https://github.com/Meinersbur approved this pull request.

LGTM

Would you like me to land it? (consider resolving the merge conflict in ReleaseNotes.txt so I don't have to do this)

https://github.com/llvm/llvm-project/pull/226163