Insightface extra paths

[Guillaume-Fgt]

In response to issue #367

I modified the insightface_loader function to have this behavior:

• check if an entry exists for an "insightface" folder inside extra_model_paths.yaml file
• if no entry (no key "insightface"), previous behavior (use insightface folder in Comfy/models)
• if multiple entries exist, select the first one as path with a logging.info message to warn the user
• if only one entry, use this one

Some remarks:

• the model is automatically downloaded by insightface package. So if you have already used Comfy/models/insightface
  before adding an entry in the yaml file, it will download it in the new place (under yaml_path/models/buffalo_l)
  So, you will have a duplication of the model and have to delete the old one manually.
• the code still have "buffalo_l" hard coded in FaceAnalysis class. So I think it doesn't adress
  @zulfadzlie remark about "antelopev2" and "buffalo_l" usage. If we want to be able to use an other insightface model
  , it should be made in an other PR I think.

[bigcat88]

@cubiq any thoughts regarding this? will you merge this PR once the conflicts will be resolved or did you want a different approach?

I would like to request the same feature support for ComfyUI_InstantID repo and I can make the PR if needed.