Separate the auto-generate logic in the LyricAutoGenerateChangeHandler.

[andy840119]

I think it might not be a good way to collect all the generators into single change handler.

Guess should remove the LyricAutoGenerateChangeHandler eventually.

[andy840119]

I think AutoGenerateSubsection should include the generator inherit the IAutoGenerateChangeHandler?
But it will not able to call the change handler if inherit other kind of IAutoGenerateChangeHandler (e.g. IAutoGenerateChangeHandler<T>)

Need more think about this.

[andy840119]

Implemented, nice.

[andy840119]

It might not be a good idea if one property has more than 2 generators.

In #2004, time-tags change handler has 2 generator

• generate the time-tags.
• generate the romaji inside the time-tags.

Guess should be better to collect all generators again.