buffer: improve copy() performance

There is no need to create a slice when sourceEnd is out of bounds.

PR-URL: #33214
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Zeyu Yang <himself65@outlook.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

Author: seishun

lib/buffer.js

@@ -257,7 +257,7 @@ function _copyActual(source, target, targetStart, sourceStart, sourceEnd) {
   if (nb > sourceLen)
     nb = sourceLen;
 
-  if (sourceStart !== 0 || sourceEnd !== source.length)
+  if (sourceStart !== 0 || sourceEnd < source.length)
     source = new Uint8Array(source.buffer, source.byteOffset + sourceStart, nb);
 
   target.set(source, targetStart);