Replace uses of ioutil

ioutil package was deprecated in Go 1.16, replace all uses with their
respective replacements.

This patch was generated with a combination of `gofmt -r`, `eg`, and
manually (for `ioutil.ReadDir`).

test/t-03-queue_persistency/addtoqueue.go

@@ -12,7 +12,7 @@ package main
 import (
 	"flag"
 	"fmt"
-	"io/ioutil"
+	"io"
 	"os"
 	"time"
 
@@ -29,7 +29,7 @@ var (
 func main() {
 	flag.Parse()
 
-	data, err := ioutil.ReadAll(os.Stdin)
+	data, err := io.ReadAll(os.Stdin)
 	if err != nil {
 		fmt.Printf("error reading data: %v\n", err)
 		os.Exit(1)

test/util/coverhtml/coverhtml.go

@@ -10,7 +10,6 @@ import (
 	"flag"
 	"fmt"
 	"html/template"
-	"io/ioutil"
 	"math"
 	"os"
 	"strings"
@@ -50,7 +49,7 @@ func main() {
 		totals.Add(p)
 
 		fname := strings.Join(strings.Split(p.FileName, "/")[*strip:], "/")
-		src, err := ioutil.ReadFile(fname)
+		src, err := os.ReadFile(fname)
 		if err != nil {
 			errorf("Failed to read %q: %v", fname, err)
 		}

test/util/fexp/fexp.go

@@ -11,7 +11,7 @@ import (
 	"crypto/x509"
 	"flag"
 	"fmt"
-	"io/ioutil"
+	"io"
 	"net/http"
 	"os"
 	"regexp"
@@ -70,13 +70,13 @@ func main() {
 		fatalf("error getting %q: %v\n", url, err)
 	}
 	defer resp.Body.Close()
-	rbody, err := ioutil.ReadAll(resp.Body)
+	rbody, err := io.ReadAll(resp.Body)
 	if err != nil {
 		errorf("error reading body: %v\n", err)
 	}
 
 	if *save != "" {
-		err = ioutil.WriteFile(*save, rbody, 0664)
+		err = os.WriteFile(*save, rbody, 0664)
 		if err != nil {
 			errorf("error writing body to file %q: %v\n", *save, err)
 		}
@@ -170,7 +170,7 @@ func mkTransport(caCert string) http.RoundTripper {
 		return nil
 	}
 
-	certs, err := ioutil.ReadFile(caCert)
+	certs, err := os.ReadFile(caCert)
 	if err != nil {
 		fatalf("error reading CA file %q: %v\n", caCert, err)
 	}