Optimize checks against close integer values.

### Description
Checks like `i == 0 || i == -1` or `i == 0 || i == -2` currently get emitted as separate checks instead of an optimal combined check.

### Configuration
any

### Regression?
no

### Data
Current codegen: https://compiler-explorer.com/z/eaGv9easn
Desired codegen from C++: https://godbolt.org/z/avq3odcoP