GOEXPERIMENT=rangefunc still enables it for all Go modules.
Otherwise only enable in Go 1.23 source files.
More work remains but it will be done in follow-up issues.
Fixes #61405.
Change-Id: Icad64942deb152ee65444e4d7be289814a8a0b6b
Reviewed-on: https://go-review.googlesource.com/c/go/+/557835 Reviewed-by: Robert Griesemer <gri@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: Robert Findley <rfindley@google.com>