Rewrite and move check_requested_models in input_check subworkflow

[jonasscheid]

Description of feature

I think we need to remove epytope from check_requested_models since we will not use the prediction interfaces anymore and implement checks for supported alleles and peptide lengths. I think we can integrate the functionality of show_supported_models also..

Question: Would it make more sense to move this altered module in the input_check subworkflow? With this we immediately catch unsupported alleles and the user can alter them before other processes are called e.g. variant prediction. That would then not be part anymore of the prepare input module draft in #205