Trainer._load_from_checkpoint - support loading multiple Peft adapters (#30505)
* Trainer: load checkpoint model with multiple adapters
* Trainer._load_from_checkpoint support multiple active adapters
* PeftModel.set_adapter does not support multiple adapters yet
* Trainer._load_from_checkpoint test multiple adapters
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Co-authored-by: Clara Luise Pohland <clara-luise.pohland@telekom.de>