Improve URI/query strings sanitization

[stsypanov]

Use StringBuilder.deleteCharAt(int) and StringBuilder.delete(int, int) to handle sanitization more effectively

[rstoyanchev]

Looks fine as far as I UriComponentsBuilder and UrlPathHelper are concerned.

Very minor, I would say getSanitizedPath and doubleToSingleSlash can be combined into one method. Also the same identical method could be created in UriComponentsBuilder. When there is identical logic it's useful to make it look as identical as possible.

[stsypanov]

@rstoyanchev done.

I've also measured performance impact with simple benchmark

@BenchmarkMode(Mode.AverageTime)
@OutputTimeUnit(TimeUnit.NANOSECONDS)
@Fork(jvmArgsAppend = {"-Xms2g", "-Xmx2g"})
public class DropDoubleSlashBenchmark {

  @Benchmark
  public String ineffective(Data data) {
    String path = data.path;
    while (true) {
      int index = path.indexOf("//");
      if (index == -1) {
        break;
      }
      path = path.substring(0, index) + path.substring(index + 1);
    }
    return path;
  }

  @Benchmark
  public String effective(Data data) {
    StringBuilder path = new StringBuilder(data.path);
    while (true) {
      int index = path.indexOf("//");
      if (index == -1) {
        break;
      }
      path.deleteCharAt(index);
    }
    return path.toString();
  }

  @State(Scope.Thread)
  public static class Data {
    private final String path = "/home/" + "/path";
  }
}

and got the following results on my machine

JDK 8

effective                          avgt    47.882 ±   1.801   ns/op
ineffective                        avgt    51.620 ±   0.907   ns/op
effective:·gc.alloc.rate.norm      avgt   136.000 ±   0.001    B/op
ineffective:·gc.alloc.rate.norm    avgt   224.000 ±   0.001    B/op

JDK 11

effective                          avgt    33.949 ±   0.188   ns/op
ineffective                        avgt    47.735 ±   0.519   ns/op
effective:·gc.alloc.rate.norm      avgt   104.000 ±   0.001    B/op
ineffective:·gc.alloc.rate.norm    avgt   152.000 ±   0.001    B/op

On longer strings I think we'll have even better improvement.

[rstoyanchev]

Thanks!