[FEAT] Add option to modify the default configure_optimizers() behavior

[JQGoh]

Rationale

• Users have asked about whether we can modify the default learning rate scheduler behaviors. See https://github.com/Nixtla/neuralforecast/issues/852#issuecomment-1961923861 and https://nixtlacommunity.slack.com/archives/C031M8RLC66/p1713516602654109
• Instead of adding arguments to all the models, passing from NeuralForecast class, we introduce a set_configure_optimizers function for the BaseModel class such that individual model can overwrite the default configure_optimizers() behavior

This shall deprecate the earlier work introduced in: https://github.com/Nixtla/neuralforecast/pull/998