refactor(types): unify InputFile with str in media types (dev-3.x)

Refactored various InputMedia types to support Union[InputFile, str] for
media properties, enhancing flexibility and unifying input data types.

- Modified media_group.py for AUDIO, PHOTO, VIDEO, and DOCUMENT.
- Updated input_media_document.py and input_media_audio.py
  to use Union[InputFile, str].
- Adjusted bot.py to utilize DateTime for close_date.
- Refactored aiohttp session for better file handle and serialization.
- Enhanced set_chat_photo.py to accept Union[InputFile, str].
- Re-organized input_file.py with modern BaseModel features.
- Added new client/form module for splitting file extraction logic.
- Adapted test cases to validate the new structure and behavior.

tests/mocked_bot.py

@@ -5,7 +5,7 @@ from aiogram import Bot
 from aiogram.client.session.base import BaseSession
 from aiogram.methods import TelegramMethod
 from aiogram.methods.base import Response, TelegramType
-from aiogram.types import UNSET_PARSE_MODE, ResponseParameters, User
+from aiogram.types import ResponseParameters, User
 
 
 class MockedSession(BaseSession):
@@ -29,7 +29,7 @@ class MockedSession(BaseSession):
         self,
         bot: Bot,
         method: TelegramMethod[TelegramType],
-        timeout: Optional[int] = UNSET_PARSE_MODE,
+        timeout: Optional[int] = None,
     ) -> TelegramType:
         self.closed = False
         self.requests.append(method)