Add a CONDConstant for passing non tensor conds to unet.

comfy/conds.py

@@ -62,3 +62,18 @@ class CONDCrossAttn(CONDRegular):
                 c = c.repeat(1, crossattn_max_len // c.shape[1], 1) #padding with repeat doesn't change result
             out.append(c)
         return torch.cat(out)
+
+class CONDConstant(CONDRegular):
+    def __init__(self, cond):
+        self.cond = cond
+
+    def process_cond(self, batch_size, device, **kwargs):
+        return self._copy_with(self.cond)
+
+    def can_concat(self, other):
+        if self.cond != other.cond:
+            return False
+        return True
+
+    def concat(self, others):
+        return self.cond