Force tx replacement price bump to zero when zero base fee market is configured (#6079)

Signed-off-by: Fabio Di Fabio <fabio.difabio@consensys.net>

util/src/main/java/org/hyperledger/besu/util/number/Percentage.java

@@ -21,6 +21,8 @@ import java.util.Objects;
 
 /** The Percentage utility. */
 public class Percentage {
+  /** Represent 0% */
+  public static final Percentage ZERO = new Percentage(0);
 
   private final int value;