Don't warn on lifetime_capture annotated method if the class object is a temporary object.

[hokein]

Example:

struct T{
 void set(const int& t [[clang::lifetime_capture_by(this)]]);
};

void s() {
    T().set(1); // we should not warn on this case.
}

[hokein]

As discussed, this is an expected behavior, see #117733.