* Refactor expression generation and substitution logic
Updated symbol naming and added safe replacement for expressions.
* Add expr_str to return values in countdown.py
Modified return statement to include the modified expression string.
* Implement test for min_numbers exceeding 10
Add test for CountdownDataset with more than 10 numbers
* Remove trailing-whitespace
* Improve readability of CountdownDataset initialization
Refactor CountdownDataset initialization for readability.
* updated medium configs
* fix problematic curriculum values / small issues causing exceptions to be raised
* optimus alpha config
* all configs so far
* fix tests
* init
* fix tests
* unify codeio
* filtered for libraries not present in reasoning-gym
* fix more bounds
* puzzle24
* knight swap curriculum
* fix number sorting
* fix attributes
* add validation of config in creation of dataset
* dry run for instantiating and validating the datasets
* remove unused imports
* fix curriculum tests to reference newly updated attribute names
