lib: optimize writable stream buffer clearing

Improved the `clearBuffer` function
by replacing `buffered.splice` with `ArrayPrototypeSlice`.
- Eliminates O(N) shifting overhead.
- Improves CPU utilization and reduces GC overhead.
PR-URL: #59406
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Ethan Arrowood <ethan@arrowood.dev>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Anna Henningsen <anna@addaleax.net>

Author: ri7116

lib/internal/streams/writable.js

@@ -784,7 +784,7 @@ function clearBuffer(stream, state) {
 if(i===buffered.length){
 resetBuffer(state);
 }elseif(i>256){
-buffered.splice(0,i);
+state[kBufferedValue]=ArrayPrototypeSlice(buffered,i);
 state.bufferedIndex=0;
 }else{
 state.bufferedIndex=i;