[llvm] [SLP] Enable full non-power-of-2 vectorization by default (PR #196825)

[Alexey Bataev via llvm-commits]

alexey-bataev wrote:

> Can you clean up these magic numbers (3 and 5) - I'm assuming to stop random regressions?

Mostly compile time tuning

https://github.com/llvm/llvm-project/pull/196825