Name conflict with auto imported `std::core`, but it should have lower priority

[cbuttner]

We talked about this briefly half a year ago, so I'm just opening an issue to keep track of it.

module my::thing;
import my::base;

fn void main() {
  log::info();
}

module my::base::log;
fn void info() {}

Error: The function 'log::info' is defined in both 'my::base::log' and 'std::core::log', please use either my::base::log::info or std::core::log::info to resolve the ambiguity.