Reland union type (#5900)

* Reapply "Add union link connection type support (#5806)" (#5889)

This reverts commit bf9a90a145.

* Fix union type breaks existing type workarounds

* Add non-string test

* Add tests for hacks and non-string types

* Support python versions lower than 3.11

execution.py

@@ -16,6 +16,7 @@ import comfy.model_management
 from comfy_execution.graph import get_input_info, ExecutionList, DynamicPrompt, ExecutionBlocker
 from comfy_execution.graph_utils import is_link, GraphBuilder
 from comfy_execution.caching import HierarchicalCache, LRUCache, CacheKeySetInputSignature, CacheKeySetID
+from comfy_execution.validation import validate_node_input
 from comfy.cli_args import args
 
 class ExecutionResult(Enum):
@@ -527,7 +528,6 @@ class PromptExecutor:
                 comfy.model_management.unload_all_models()
 
 
-
 def validate_inputs(prompt, item, validated):
     unique_id = item
     if unique_id in validated:
@@ -589,8 +589,8 @@ def validate_inputs(prompt, item, validated):
             r = nodes.NODE_CLASS_MAPPINGS[o_class_type].RETURN_TYPES
             received_type = r[val[1]]
             received_types[x] = received_type
-            if 'input_types' not in validate_function_inputs and received_type != type_input:
-                details = f"{x}, {received_type} != {type_input}"
+            if 'input_types' not in validate_function_inputs and not validate_node_input(received_type, type_input):
+                details = f"{x}, received_type({received_type}) mismatch input_type({type_input})"
                 error = {
                     "type": "return_type_mismatch",
                     "message": "Return type mismatch between linked nodes",