basic_istream::read/basic_istream::read_some and basic::ostream::write should be marked with [[clang::unsafe_buffer_usage]]

https://godbolt.org/z/e77vEEz7h

```cpp
#include <iostream>
#include <array>

auto f(std::ostream &st, char *p, std::size_t s) {
    st.write(p, s);
}

auto g(std::istream &st, char *p, std::size_t s) {
    st.read(p, s);
}

int main() {
    std::array<char, 1> a;
    f(std::cout, a.data(), 100);
    g(std::cin, a.data(), 100);
}
```