Prefer a `for`-statement to a `while`-statement when there is an obvious loop variable

Reason

Readability: the complete logic of the loop is visible "up front". The scope of the loop variable can be limited.

Example

for (gsl::index i = 0; i < vec.size(); i++) {
    // do work
}

Example, bad

int i = 0;
while (i < vec.size()) {
    // do work
    i++;
}

Enforcement

???