* Refactor and optimize cellseqs_v2 in Nim standard library
* Extract resizing logic into a separate 'resize' procedure for better readability and separation of concerns
* Implement realloc for non-threaded cases to improve memory operations efficiency
* Use ',' instead of ';' between parameters in 'add' procedure for consistency with other Nim code
* Respond to Araq's feedback: Refactor resize function to use reallocShared
This commit replaces the usage of allocShared and deallocShared with reallocShared to optimize memory allocation and deallocation while resizing the CellSeq.