cleanup for Stan draw files

[stemangiola]

• Introduced cleanup_draw_files parameter in sccomp_estimate() and sccomp_remove_outliers() to automatically delete large Stan draw CSV files after analysis, reducing disk space usage.
• Added new clear_draw_files() function for manual cleanup of draw files with flexible filtering options.
• Updated documentation and NEWS file to reflect these changes.

[Copilot]

@stemangiola I've opened a new pull request, #245, to work on those changes. Once the pull request is ready, I'll request review from you.