Related command
apim api export

Is your feature request related to a problem? Please describe.
some teams may need to export their api spec with a certain file name to be compatible with existing codegen/scripts

Describe the solution you'd like
add --file-name to save the eported file to a specified file name

Describe alternatives you've considered
the alternative it to manually rename the file which is automatically saved as f"{api_id}_{exportType}{file_extension}"

Additional context
This will enable teams to manually download swagger specs and import them into their codebase for use with codegen to instead run az apim export from their package.json and automatically codegen based on the filename already in their scripts.