Remove extra indirection from statics with linkage?

I just learned from @bjorn3 that the way we represent statics with linkage, such as #[linkage = "extern_weak"], is kind of strange:

unsafe extern "C" {
    #[linkage = "extern_weak"]
    static test_symbol_that_does_not_exist: Option<unsafe extern "C" fn()>;
}

Here, test_symbol_that_does_not_exist will actually be a global variable local to this module that points to the weak symbol.

Now that we have the &raw address-of operator, we could avoid this extra indirection. Whether we should, I do not know.
Cc @bjorn3 @nikic @chorman0773

Start with the #[linkage = "extern_weak"] example and the &raw address-of operator mentioned in the issue. Determine whether statics with linkage can avoid the module-local pointer, then define the affected behavior and validation before proposing a change; no files or tests are named.