lint: enable intrange linter (#7331)

Enable intrange linter to enforce modern Go range syntax over
traditional for loops, by converting:

for i := 0; i < n; i++

to:

for i := range n

Adding type conversions where needed for compatibility
with existing uint64 parameters.

Signed-off-by: Ville Vesilehto <ville@vesilehto.fi>

plugin/file/file_test.go

@@ -6,7 +6,7 @@ import (
 )
 
 func BenchmarkFileParseInsert(b *testing.B) {
-	for i := 0; i < b.N; i++ {
+	for range b.N {
 		Parse(strings.NewReader(dbMiekENTNL), testzone, "stdin", 0)
 	}
 }