S3 Select: optimize output (#8238)

Queue output items and reuse them.
Remove the unneeded type system in sql and just use the Go type system.

In best case this is more than an order of magnitude speedup:

```
BenchmarkSelectAll_1M-12    	       1	1841049400 ns/op	274299728 B/op	 4198522 allocs/op
BenchmarkSelectAll_1M-12    	      14	  84833400 ns/op	169228346 B/op	 3146541 allocs/op
```

pkg/s3select/select_benchmark_test.go

@@ -103,6 +103,7 @@ func benchmarkSelect(b *testing.B, count int, query string) {
 
 	b.ResetTimer()
 	b.ReportAllocs()
+	b.SetBytes(int64(count))
 
 	b.RunParallel(func(pb *testing.PB) {
 		for pb.Next() {
@@ -147,6 +148,30 @@ func BenchmarkSelectAll_10M(b *testing.B) {
 	benchmarkSelectAll(b, 10*humanize.MiByte)
 }
 
+func benchmarkSingleCol(b *testing.B, count int) {
+	benchmarkSelect(b, count, "select id from S3Object")
+}
+
+// BenchmarkSingleRow_100K - benchmark SELECT column function with 100k records.
+func BenchmarkSingleCol_100K(b *testing.B) {
+	benchmarkSingleCol(b, 1e5)
+}
+
+// BenchmarkSelectAll_1M - benchmark * function with 1m records.
+func BenchmarkSingleCol_1M(b *testing.B) {
+	benchmarkSingleCol(b, 1e6)
+}
+
+// BenchmarkSelectAll_2M - benchmark * function with 2m records.
+func BenchmarkSingleCol_2M(b *testing.B) {
+	benchmarkSingleCol(b, 2e6)
+}
+
+// BenchmarkSelectAll_10M - benchmark * function with 10m records.
+func BenchmarkSingleCol_10M(b *testing.B) {
+	benchmarkSingleCol(b, 1e7)
+}
+
 func benchmarkAggregateCount(b *testing.B, count int) {
 	benchmarkSelect(b, count, "select count(*) from S3Object")
 }