Promote reflections of references to complete objects to their entities

[katzdm]

Given:

int val = 3;
constexpr auto r = std::meta::reflect_result<int &>(val);

The reflection r should be "promoted" to reflect the entity val. That is, the following should hold:

static_assert(r == ^val);

As of now, it's instead being stored as an RK_const_value whose expression is an lvalue - it should "promote" to an RK_declaration.

[katzdm]

Closed by 43bf5b8.