* AIR: add `mod` instruction for modulus division
- Implement for LLVM backend
* Sema: implement `@mod`, `@rem`, and `%`.
* Sema: fix comptime switch evaluation
* Sema: implement comptime shift left
* Sema: fix the logic inside analyzeArithmetic to handle all the
nuances between the different mathematical operations.
- Implement comptime wrapping operations