Improve Cleanup Session Temporary Files

[AmmarAbouZor]

Chipmunk writes session temporary files to the directory tmp in chipmunk home directory, and those files seems to not be cleaned up always + attachment files never get cleaned up. Therefore, it would be better to consider some improvements on the cleaning up mechanism.
Here are some suggestions:

• Remove session main file and the attachments directory on drop() method on Rust side, to ensure file will be cleaned up even on panics.
• Move the temporary directory to the Operating system temporary directory, so at least they would get cleaned up once the user (or the operating system) cleaned up the temporary directory
• Clean up the temp directory when chipmunk starts, but we need to solve the issue if multiple Chipmunk instance are running on the same device
• Provide a function inside Chipmunk to clean up temporary data, but I don't know how affective this solution would be, because the user may never see or use such a function.