Delegate readString in FilterStreamInput to possibly use an optimized…

… readString of the delegate. (elastic#105712)

This is necessary so that the optimized `readString` added in
elastic#104692 is actually used
when wrapped in a `FilterStreamInput`.

server/src/main/java/org/elasticsearch/common/io/stream/FilterStreamInput.java

@@ -26,6 +26,11 @@ protected FilterStreamInput(StreamInput delegate) {
         this.delegate = delegate;
     }
 
+    @Override
+    public String readString() throws IOException {
+        return delegate.readString();
+    }
+
     @Override
     public byte readByte() throws IOException {
         return delegate.readByte();

server/src/main/java/org/elasticsearch/index/translog/BufferedChecksumStreamInput.java

@@ -48,6 +48,11 @@ public long getChecksum() {
         return this.digest.getValue();
     }
 
+    @Override
+    public String readString() throws IOException {
+        return doReadString(readArraySize()); // always use the unoptimized slow path
+    }
+
     @Override
     public byte readByte() throws IOException {
         final byte b = delegate.readByte();