[clang-tidy] Request: flag unused result of ternary operator with side effects

```c++
#include

int main(int argc, char* argv[]) {
argc ? std::cout << "true" : std::cout << "false";
}
```
https://godbolt.org/z/qq4j1zbob

Somewhat related: https://github.com/llvm/llvm-project/issues/34348

Start with the C++ reproducer in the issue and the linked Compiler Explorer example, then inspect existing clang-tidy checks for unused expression results and the related issue #34348. Done means clang-tidy reports the unused ternary result when its branches have side effects, with coverage for the shown case.

Written by the indexing model from the issue text.