MM-52532: Fix golangci warnings (#23709)

https://mattermost.atlassian.net/browse/MM-52532

- Replace golint with revive
- Add makezero linter
- Fix all the required linter failures

Some issues in enterprise and public modules
are yet to be fixed. We send this to expediate things.

server/platform/services/httpservice/client.go

@@ -89,7 +89,7 @@ func init() {
 
 type DialContextFunction func(ctx context.Context, network, addr string) (net.Conn, error)
 
-var AddressForbidden error = errors.New("address forbidden, you may need to set AllowedUntrustedInternalConnections to allow an integration access to your internal network")
+var AddressForbidden = errors.New("address forbidden, you may need to set AllowedUntrustedInternalConnections to allow an integration access to your internal network")
 
 func dialContextFilter(dial DialContextFunction, allowHost func(host string) bool, allowIP func(ip net.IP) bool) DialContextFunction {
 	return func(ctx context.Context, network, addr string) (net.Conn, error) {

server/platform/shared/filestore/filesstore_test.go

@@ -487,10 +487,7 @@ func (s *FileBackendTestSuite) TestAppendFile() {
 	s.Run("should correctly append the data", func() {
 		// First part needs to be at least 5MB for the S3 implementation to work.
 		size := 5 * 1024 * 1024
-		b := make([]byte, size)
-		for i := range b {
-			b[i] = 'A'
-		}
+		b := bytes.Repeat([]byte{'A'}, size)
 		path := "tests/" + randomString()
 
 		written, err := s.backend.WriteFile(bytes.NewReader(b), path)