[llvm] [RISCV][RFC] Enable store clustering by default (PR #73796)

[Alex Bradbury via llvm-commits]

asb wrote:

I've force pushed a rebase on top of the latest #77389. The difference vs before is that clustered memory operations are consistently sorted (see [here](https://github.com/llvm/llvm-project/pull/73789#issuecomment-1842994094) for more details).

https://github.com/llvm/llvm-project/pull/73796