feat: generate smaller variable names

[Aenimus]

Currently, the 27th variable will be aa but the 53rd will be aaa. This means the size of the variable grows quickly.

In this approach, the variable names grows much slower:
a, ..., z, aa, ..., az, ba, ..., zz, aaa, aab, ...

2 chars at 27 variables,
3 chars at 703 variables,
4 chars at 18279 variables, etc.