Restructure the Custom Abundance Widget module

[yuyizheng1112]

The custom abundance widget has developed various functionality as the project progressed. It requires more data and information than anticipated. Thus, I'm going to restructure the code so that it can be easier to develop and maintain. I'm planning to separate the data from the widget. And new tests should be added after restructuring.
This work will be done after GSoC.

[jaladh-singhal]

@yuyizheng1112 can we close it? Or are there still more things you want to restructure?

[yuyizheng1112]

Sure. Thanks for the reminder! @jaladh-singhal