Range index does not create buckets correctly for `FLOAT` columns

[richardstartin]

When there is a range index on a FLOAT column, all values may be grouped under the same bucket whenever all values have the same integer floor value.

This is caused by a bug in persisting the floating point data, where the value is converted to an integer:

  private static class FloatValueBuffer implements NumberValueBuffer {
    private final PinotDataBuffer _dataBuffer;

    FloatValueBuffer(PinotDataBuffer dataBuffer) {
      _dataBuffer = dataBuffer;
    }

    @Override
    public void put(int position, Number value) {
      _dataBuffer.putFloat(position << 2, value.intValue()); // oops!
    }

    @Override
    public Number get(int position) {
      return _dataBuffer.getFloat(position << 2);
    }

    @Override
    public int compare(Number val1, Number val2) {
      return Float.compare(val1.floatValue(), val2.floatValue());
    }
  }

The current test for the RangeIndexCreator passes because it uses RangeIndexCreator._rangeStartArray as part of the test set up, so doesn't catch that RangeIndexCreator._rangeStartArray only has one element:

[richardstartin]

Fixed by #7435