PerformanceInliner: always inline synthesized enum comparisons if one of the operands is a constant enum
If there is a "constant" enum argument to a synthesized enum comparison, we can always inline it, because most of it will be constant folded anyway.
This ensures the compiler is not creating terrible code for very simple enum comparisons, like
```
if someEnum == .someCase {
...
}
```
rdar://85677499