Operators for alias columns, alias columns from column pointers

[trueqbit]

This PR further simplifies working with alias columns.

• Alias columns can be made from a derived object member pointer without forming an explicit column pointer. E.g. instead of writing alias_column<alias_a<Derived>>(column<Derived>(&Object::field)) one can simply write alias_column<alias_a<Derived>>(&Object::field).
• The convenience pointer-to-member operator operator->*() now also checks whether object type of a member pointer is the same as the aliased type, just like the named function alias_column().
  E.g. this means that "my"_alias.for_<Object>()->*&Object::field works, but "xyz"_alias.for_<Something>()->*&Object::field does not.
• Overloaded operators for alias columns. One can write e.g. alias_column<myalias>(&Object::id) == 4 without "lifting" 4 into an expression using c(4), which improves legibility.

Additionally:

• Column pointers and alias columns can now be used as constant expressions. This IMO improves the ability to create short definitions for long expressions that can be reused afterwards.
  E.g. constexpr auto reuseColumn = column_pointer<Derived>(&Object::id); or constexpr auto aliasedColumn = alias_column<alias_a<Derived>>(&Object::id);.
• Updated vcpkg test environment on appveyor to tag "2023.10.19".