[display] make @position work at the end of type path for ENew (see #2995)

We talked with @Simn about how to make --display @ position work with `new MyClass()` at the end of type path, instead of the end of whole expression (so it has the same behaviour as other type-position queries and doesn't make IDE authors' life a nightmare). I researched it a bit and came up with this simple solution - in a display mode, wrap the `ENew` in an internal `EMeta` positioned at the end of type path, so `typeload.ml` catch it later.

I'm not sure if this solution is sane, but it seems pretty simple and non-invasive. :wink: