🔒 chore(loading.py): remove code that deletes files after loading in instantiate_documentloader function

The save_uploaded_file function now uses the folder_name parameter instead of file_name to improve semantics. The appdirs library is now used to get the user cache directory and a folder for langflow cache is created. The sha256 hash of the file content is now used as the file name to avoid collisions and improve security. A folder is now created for each flow_id in the save_uploaded_file function. The code that deletes files after loading in the instantiate_documentloader function has been removed as it is unnecessary and can cause issues.
🐛 fix(endpoints.py): change file_name parameter to folder_name in save_uploaded_file function
🔒 chore(utils.py): use appdirs to get user cache directory and create a folder for langflow cache
🔒 chore(utils.py): use sha256 hash of file content as file name to avoid collisions and improve security
🔒 chore(utils.py): create folder for each flow_id in save_uploaded_file function