Language Server: Return suggestions for compatible types

[farmaazon]

General Summary

Currently when Language Server is asked for suggestions for Integer methods this way:

{"jsonrpc":"2.0","id":16,"method":"search/completion","params":{"file":{"rootId":"c9e6b9e9-9009-4c17-9a22-a876c2332836","segments":["src","Main.enso"]},"position":{"character":6,"line":4},"returnType":null,"selfType":"Builtins.Main.Integer","tags":null}}

We receive a single suggestion of method up_to. The other compatible methods (e.g. those of Number) should be returned as well.

Motivation

This is to answer the IDE bug report: https://github.com/enso-org/ide/issues/1140