[Feature] Use pydantic validation in lora.py and load.py configs (#26413)

Signed-off-by: simondanielsson <simon.danielsson99@hotmail.com>

vllm/config/utils.py

@@ -11,6 +11,7 @@ from itertools import pairwise
 from typing import TYPE_CHECKING, Any, Protocol, TypeVar
 
 import regex as re
+from pydantic.fields import FieldInfo
 from typing_extensions import runtime_checkable
 
 if TYPE_CHECKING:
@@ -50,7 +51,14 @@ def get_field(cls: ConfigType, name: str) -> Field:
     if (default_factory := named_field.default_factory) is not MISSING:
         return field(default_factory=default_factory)
     if (default := named_field.default) is not MISSING:
+        if isinstance(default, FieldInfo):
+            # Handle pydantic.Field defaults
+            if default.default_factory is not None:
+                return field(default_factory=default.default_factory)
+            else:
+                default = default.default
         return field(default=default)
+
     raise ValueError(
         f"{cls.__name__}.{name} must have a default value or default factory."
     )