perf(gnolang): make print+println much more efficient

This change is the result of seeing print/println being
reported in bugs as needing gas metering but on examination,
noticed that the code causes a RAM and CPU bloat, so this
makes an improvement in all dimensions

```shell
$ benchstat before_println.txt after_println3.txt
name          old time/op    new time/op    delta
GnoPrintln-8    1.94ms ± 2%    1.86ms ± 4%   -4.02%  (p=0.001 n=9+9)

name          old alloc/op   new alloc/op   delta
GnoPrintln-8    1.92MB ± 0%    1.81MB ± 0%   -5.92%  (p=0.000 n=10+10)

name          old allocs/op  new allocs/op  delta
GnoPrintln-8     19.0k ± 0%     16.0k ± 0%  -15.76%  (p=0.002 n=8+10)
```

Fixes #3951

Author: odeke-em

gnovm/pkg/gnolang/uverse.go

@@ -2,6 +2,7 @@ package gnolang
 
 import (
 	"fmt"
+	"io"
 	"strings"
 
 	bm "github.com/gnolang/gno/gnovm/pkg/benchops"
@@ -718,16 +719,30 @@ func makeUverseNode() {
 			arg0 := m.LastBlock().GetParams1()
 			xv := arg0
 			xvl := xv.TV.GetLength()
-			ss := make([]string, xvl)
-			for i := 0; i < xvl; i++ {
-				ev := xv.TV.GetPointerAtIndexInt(m.Store, i).Deref()
-				ss[i] = ev.Sprint(m)
-			}
-			rs := strings.Join(ss, " ")
-			if debug {
-				print(rs)
+
+			switch debug {
+			case true:
+				ss := make([]string, xvl)
+				for i := 0; i < xvl; i++ {
+					ev := xv.TV.GetPointerAtIndexInt(m.Store, i).Deref()
+					ss[i] = ev.Sprint(m)
+				}
+				rs := strings.Join(ss, " ")
+				if debug {
+					print(rs)
+				}
+				io.WriteString(m.Output, rs)
+
+			default:
+				max := xvl - 1
+				for i := 0; i < xvl; i++ {
+					ev := xv.TV.GetPointerAtIndexInt(m.Store, i).Deref()
+					io.WriteString(m.Output, ev.Sprint(m))
+					if i < max {
+						io.WriteString(m.Output, " ")
+					}
+				}
 			}
-			m.Output.Write([]byte(rs))
 		},
 	)
 	defNative("println",
@@ -739,16 +754,40 @@ func makeUverseNode() {
 			arg0 := m.LastBlock().GetParams1()
 			xv := arg0
 			xvl := xv.TV.GetLength()
-			ss := make([]string, xvl)
-			for i := 0; i < xvl; i++ {
-				ev := xv.TV.GetPointerAtIndexInt(m.Store, i).Deref()
-				ss[i] = ev.Sprint(m)
+
+			if xvl == 0 {
+				// Mimick Go in which invoking println() does nothing.
+				return
 			}
-			rs := strings.Join(ss, " ") + "\n"
-			if debug {
-				println("DEBUG/stdout: " + rs)
+
+			max := xvl - 1
+
+			switch debug {
+			case true:
+				ss := make([]string, xvl)
+				for i := 0; i < xvl; i++ {
+					ev := xv.TV.GetPointerAtIndexInt(m.Store, i).Deref()
+					ss[i] = ev.Sprint(m)
+				}
+				println("DEBUG/stdout: " + strings.Join(ss, " ") + "\n")
+				for i, segment := range ss {
+					io.WriteString(m.Output, segment)
+					if i < max {
+						io.WriteString(m.Output, " ")
+					}
+				}
+			default:
+				for i := 0; i < xvl; i++ {
+					ev := xv.TV.GetPointerAtIndexInt(m.Store, i).Deref()
+					io.WriteString(m.Output, ev.Sprint(m))
+					if i < max {
+						io.WriteString(m.Output, " ")
+					}
+				}
 			}
-			m.Output.Write([]byte(rs))
+
+			io.WriteString(m.Output, "\n")
+
 		},
 	)
 	defNative("recover",