[llvm] [RISCV] Enable TTI::shouldDropLSRSolutionIfLessProfitable by default (PR #89927)

[Alex Bradbury via llvm-commits]

asb wrote:

Although blocked on #89924 moving the option to a hook, I'd be interested if anyone has any feedback or thoughts on this direction. Dropping LSR solutions that our metrics deem unprofitable, and working to improve the heuristics if that causes any unexpected degradation seems sensible to me. But there may be history with work in this area I'm not aware of.

https://github.com/llvm/llvm-project/pull/89927