…ons.rs)

Add test functions for Sqlean extensions (vss0, math0, fuzzy0, stats0)

- Added tests to extensions.rs for the following Sqlean extensions:
  - vss0: Vector similarity search
  - math0: Mathematical functions (e.g., sin(PI / 2))
  - fuzzy0: String distance (e.g., Levenshtein distance)
  - stats0: Statistical operations (e.g., calculating averages)
  
- Tests include creating sample tables, executing relevant SQL queries, and verifying the functionality of each extension.