PEFT / Trainer: Make use of model.active_adapters() instead of deprecated model.active_adapter whenever possible

[younesbelkada]

As per title and as mentioned offline by @BenjaminBossan, model.active_adapter will be deprecated soon, let's make sure to slowly force Trainer to fallback into model.active_adapters instead

cc @BenjaminBossan @amyeroberts

[BenjaminBossan]

Thanks for adding this in a backwards compatible way.

Do we plan to one day require a min PEFT version that would make this extra check unnecessary? If yes, we could add a # TODO comment to the code that can be removed.

[HuggingFaceDocBuilderDev]

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[amyeroberts]

Thanks for handling the deprecation!