Replace deprecated ioutil with io and os (#20776)

* Replace ioutil with io and os

* Replace ioutil in utils/file.go

* Minor fix to tests and excluded files

Co-authored-by: Tim Scheuermann <tim.scheuermann@mattermost.com>
Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

services/remotecluster/sendmsg.go

@@ -8,7 +8,7 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
-	"io/ioutil"
+	"io"
 	"net/http"
 	"net/url"
 	"os"
@@ -163,7 +163,7 @@ func (rcs *Service) sendFrameToRemote(timeout time.Duration, rc *model.RemoteClu
 		return nil, err
 	}
 	defer resp.Body.Close()
-	body, err = ioutil.ReadAll(resp.Body)
+	body, err = io.ReadAll(resp.Body)
 	if err != nil {
 		return nil, err
 	}