cmd/compile: use very high budget for once-called closures

cmd/compile: use very high budget for once-called closures

This should make it much more likely that rangefunc
iterators become "plain inline code".

Change-Id: I8026603afdc5249f60cc663c4bc15cb1d26d1c83
Reviewed-on: https://go-review.googlesource.com/c/go/+/630696
Reviewed-by: Keith Randall <khr@golang.org>
Auto-Submit: David Chase <drchase@google.com>
Reviewed-by: Keith Randall <khr@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>