Comprehensive Enhancements and Improvements

[cloner174]

This pull request encompasses a wide range of enhancements to the Dataset_Custom class, Exp_Informer class and perhaps a few other classes to enhance their functionality, adaptability and customization, for different use cases. The changes include adjustments to parameter defaults, introduction of new parameters, enabling detailed tracking of performance metrics and improvements in the data scaling process.

For more detailed information, please refer to: https://github.com/cloner174/Informer2020/blob/main/NewChanges.md