Replace most usages of ioutil with the underlying function

The ioutil functions are deprecated since Go 1.17 and only wrap another
library function. Thus directly call the underlying function.

This commit only mechanically replaces the function calls.

internal/cache/cache.go

@@ -2,7 +2,6 @@ package cache
 
 import (
 	"fmt"
-	"io/ioutil"
 	"os"
 	"path/filepath"
 	"regexp"
@@ -26,7 +25,7 @@ const dirMode = 0700
 const fileMode = 0644
 
 func readVersion(dir string) (v uint, err error) {
-	buf, err := ioutil.ReadFile(filepath.Join(dir, "version"))
+	buf, err := os.ReadFile(filepath.Join(dir, "version"))
 	if errors.Is(err, os.ErrNotExist) {
 		return 0, nil
 	}
@@ -130,7 +129,7 @@ func New(id string, basedir string) (c *Cache, err error) {
 	}
 
 	if v < cacheVersion {
-		err = ioutil.WriteFile(filepath.Join(cachedir, "version"), []byte(fmt.Sprintf("%d", cacheVersion)), fileMode)
+		err = os.WriteFile(filepath.Join(cachedir, "version"), []byte(fmt.Sprintf("%d", cacheVersion)), fileMode)
 		if err != nil {
 			return nil, errors.WithStack(err)
 		}