Better discoverability for members in constructors (Tooling)

[SchlenkR]

This request is related to: #9534 and fsharp/fslang-suggestions#880

I suggest that assignable class members are shown on top of the auto completion list when the caret is inside of an object constructor. Right now, the list is filled with keywords, members, symbols in scope in an alphabetical order.

Here is an example using Plotly:

[cartermp]

Specifically this request is for when ctrl+space is triggered explicitly, since the type in question has no parameters for its constructor and thus Signature Help would have nothing to display.

[kerams]

This is very doable, but requires a refactoring of the completion sorting code, which is currently a clusterfu...mess.