cmd/compile,internal/runtime/maps: add extendible hashing

cmd/compile,internal/runtime/maps: add extendible hashing

Extendible hashing splits a swisstable map into many swisstables. This
keeps grow operations small.

For #54766.

Cq-Include-Trybots: luci.golang.try:gotip-linux-ppc64_power10,gotip-linux-amd64-longtest-swissmap
Change-Id: Id91f34af9e686bf35eb8882ee479956ece89e821
Reviewed-on: https://go-review.googlesource.com/c/go/+/604936
Reviewed-by: Keith Randall <khr@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Keith Randall <khr@google.com>