Support base SDXL and SDXL refiner models.

Large refactor of the model detection and loading code.

comfy/ldm/modules/attention.py

@@ -600,7 +600,7 @@ class SpatialTransformer(nn.Module):
                  use_checkpoint=True, dtype=None):
         super().__init__()
         if exists(context_dim) and not isinstance(context_dim, list):
-            context_dim = [context_dim]
+            context_dim = [context_dim] * depth
         self.in_channels = in_channels
         inner_dim = n_heads * d_head
         self.norm = Normalize(in_channels, dtype=dtype)
@@ -630,7 +630,7 @@ class SpatialTransformer(nn.Module):
     def forward(self, x, context=None, transformer_options={}):
         # note: if no context is given, cross-attention defaults to self-attention
         if not isinstance(context, list):
-            context = [context]
+            context = [context] * len(self.transformer_blocks)
         b, c, h, w = x.shape
         x_in = x
         x = self.norm(x)