Allow override of folder_paths.base_path via env var

[webfiltered]

• Allows the configuration of the default ComfyUI folders via environment variable.
• Provides a number of the pre-requisites for ComfyUI to be executed from a read-only location.
• Covers additional folders with Remove redundant code from folder_paths #6576.
• No change if env var is not set.

[robinjhuang]

This will allow custom nodes to reference models that are placed in directories other than the default ComfyUI/models. Needed in configurations like the desktop app.

eg. ComfyUI-HunyuanVideoWrapper

clip_model_path = os.path.join(folder_paths.models_dir, "clip", "clip-vit-large-patch14")
            if not os.path.exists(clip_model_path):

[iwr-redmond]

The custom_nodes and, possibly more importantly, models_dir/configs folders both have preloaded files that I assume will need to remain available. Shouldn't there be a copy process if the env var is set (default -> override), or alternatively, some additional code to add these standard folders back as extra paths?

[robinjhuang]

The custom_nodes and, possibly more importantly, models_dir/configs folders both have preloaded files that I assume will need to remain available. Shouldn't there be a copy process if the env var is set (default -> override), or alternatively, some additional code to add these standard folders back as extra paths?

In the desktop app we can definitely add those model config files to the search path automatically. In core, I don't think that is necessary.