(Maybe for Arena as well)

Sometimes we need to duplicate a string on the resource:

    ResourceArea rm;
    const char* s = complex_operation();
    const char* mycopy = strcpy(ResourceArea::allocate(strlen(s)+1), s);

This often happens when the lifecycle of s is not controlled by the caller (e.g., it could be deallocated outside of the caller control), so we make a resource copy and hold on to it as long as we need it.

For simplification, we should have something like this:

    ResourceArea rm;
    const char* mycopy = ResourceArea::strdup(complex_operation());