ref ternary must match val-escapes on its branches (not ref escapes)

[VSadov]

The spec and implementation need to be updated. The following should fail

public class C
{
    bool flag1 = true;
    bool flag2 = false;

    public void M(ref Span<int> global)
    {
        Span<int> local = stackalloc int[10];

        ref var r1 = ref (flag1 ? ref global : ref local);
        ref var r2 = ref (flag2 ? ref global : ref local);

	// same as         global = local;   which would be an error.
       // but we can’t fail here, since r1 and r2 are basically the same, 
       // so should fail when making r1 and r2 above.
        r1 = r2;   

        // it would require val-escape scopes for r1 and r2 be different.
        // easier to say that val-escape must match
    }
}