give state dict creation its own method in IP-adapter pipeline tests

[sayakpaul]

For models we use a method in the test Mixin that the models can override to generate the necessary state dict. Let's follow that convention here as well

diffusers/tests/models/testing_utils/ip_adapter.py

Line 76 in a8c33fe

def create_ip_adapter_state_dict(self, model):

Override in the specific model class:

diffusers/tests/models/transformers/test_models_transformer_flux.py

Line 322 in a8c33fe

return create_flux_ip_adapter_state_dict(model)

Originally posted by @DN6 in #14622 (comment)