修改了averageTone 的计算方法，优化 Modulation Plus的效果，基本上不跑调了

[xiaobaijunya]

Optimize averageTone for better Modulation Plus effect
使用dio或者pyin算法生成一个frq会得到最佳效果（因为有些frq会把无声区也弄一个非常奇怪的f0，这时候可能计算的没那么好了）
读取音素oto区域的frq，去除最高和最低的30%的f0，然后计算出来一个平均的f0数值作为中间值，相较于之前的直接获取frq的整个音频的f0均值，这样能避免跑调了

[maiko3tattun]

It cannot be said definitively that this method is superior. In cases where the original audio has a pitch scoop or pronounced vibrato, this method may be less accurate than the current implementation, which uses the average value specified in the frq file. While users can edit the average pitch in the frq file, this method does not provide a way for users to correct pitch deviations.

0.1.569 (current beta)

This PR

[maiko3tattun]

There are even more striking examples.

0.1.569

This PR

There is also the issue that the calculations take a long time. At the very least, I think this should be an optional feature.

[maiko3tattun]

To be honest, I've tried a similar approach myself, so I understand what you're trying to do. However, it's difficult to pull off.

[xiaobaijunya]

I understand. Thanks for your reply.