🌱 implement basic rate limiting for best practices worker. (#4090)

We are getting connection reset requests from bestpractices.dev and 429
errors from our GCS bucket for too many writes. The GCS limit (1000 QPS)
is much higher, so just use the bestpractices.dev limit of 1 QPS.
https://github.com/coreinfrastructure/best-practices-badge/blob/main/docs/api.md

The construct was taken from https://go.dev/wiki/RateLimiting which "works well
for rates up to tens of operations per second."

Signed-off-by: Spencer Schrock <sschrock@google.com>

cron/internal/cii/main.go

@@ -24,6 +24,7 @@ import (
 	"log"
 	"net/http"
 	"strings"
+	"time"
 
 	"github.com/ossf/scorecard/v5/clients"
 	"github.com/ossf/scorecard/v5/cron/config"
@@ -95,9 +96,13 @@ func main() {
 		panic(err)
 	}
 
+	throttle := time.NewTicker(time.Second) // bestpractices.dev wants 1 QPS
+	defer throttle.Stop()
+
 	pageNum := 1
 	pageResp, err := getPage(ctx, pageNum)
 	for err == nil && len(pageResp) > 0 {
+		<-throttle.C
 		if err := writeToCIIDataBucket(ctx, pageResp, ciiDataBucket); err != nil {
 			panic(err)
 		}