Kernel prepatch 6.9-rc3

Ok, so this rc3 looks a bit different than the usual ones, because there's a large series to bcachefs to do filesystem repair after corruption. Not normally something we'd see in an rc kernel, but hey, if you had a corrupted bcachefs filesystem you'd probably want this, and if you thought bcachefs was stable already, I have a bridge to sell you. Special deal only for you, real cheap.