all: create swissmap experiment and fork files

all: create swissmap experiment and fork files

The _swiss.go files are identical to the originals (except build tag).
Later CLs will change them.

For #54766.

Cq-Include-Trybots: luci.golang.try:gotip-linux-amd64-longtest-swissmap
Change-Id: I9943e2d6f1cfa227ffbf27c9ddc9ce853695d225
Reviewed-on: https://go-review.googlesource.com/c/go/+/580778
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Keith Randall <khr@golang.org>
Auto-Submit: Michael Pratt <mpratt@google.com>
Commit-Queue: Michael Pratt <mpratt@google.com>
Reviewed-by: Keith Randall <khr@google.com>