Replace CLIPType if with getattr

[city96]

This is mostly a small change that replaces the long if statement with a getattr where the common name (e.g. "wan") gets mapped to the enum (CLIPType.WAN) in the clip loader nodes.

The main benefit of this is assuring that the common name actually matches the enum, so that downstream nodes don't need to keep their own mapping for custom clip loader nodes. (ref: city96/ComfyUI-GGUF#246 (comment))

Test for the current values in the single / dual clip loader node. Only odd one out is SDXL which doesn't have an enum and instead uses "stabe_diffusion". The logic in the single clip loader node already defaults to CLIPType.STABLE_DIFFUSION, so I just extended this to the dual clip loader as well.

test = lambda type: getattr(comfy.sd.CLIPType, type.upper(), comfy.sd.CLIPType.STABLE_DIFFUSION)

[test(x) for x in ["stable_diffusion", "stable_cascade", "sd3", "stable_audio", "mochi", "ltxv", "pixart", "cosmos", "lumina2", "wan"]]
# returns: [<CLIPType.STABLE_DIFFUSION: 1>, <CLIPType.STABLE_CASCADE: 2>, <CLIPType.SD3: 3>, <CLIPType.STABLE_AUDIO: 4>, <CLIPType.MOCHI: 7>, <CLIPType.LTXV: 8>, <CLIPType.PIXART: 10>, <CLIPType.COSMOS: 11>, <CLIPType.LUMINA2: 12>, <CLIPType.WAN: 13>]

[test(x) for x in ["sdxl", "sd3", "flux", "hunyuan_video"]]
# returns: [<CLIPType.STABLE_DIFFUSION: 1>, <CLIPType.SD3: 3>, <CLIPType.FLUX: 6>, <CLIPType.HUNYUAN_VIDEO: 9>]