refactor: improve ZUI standard library initialization

This commit enhances the ZUI standard library initialization by refactoring the code in `stdlib.lzui`. The changes introduce consistency in the variable naming conventions, fix a typo, and optimize the code structure.

The improvements ensure that ZUI applications have better readability and maintainability.
No issues

Signed-off-by: Salvydas Lukosius <ss-o@users.noreply.github.com>

Author: ss-o