feat(autocompletion): support nested variables

[marstamm]

This adds support for pathExpression suggestions, including pathExpressions with lists

[marstamm]

I will move this back to "In progress" as I found one requirement missing when working on Variable merging: we can merge types to "any", but not for lists. I will rework the PR to allow an entry to allow both List and Context entries for ambiguous definitions

[marstamm]

d268bcc addresses the list optional problem.

It does not support all options, as Context and array need to have the same entries. Problem e.g.: "List | Context< foo: string >" will suggest foo on input[0]., even though the List would not be of complex objects.

I could not find a satisfactory variable schema that supports both. However, overlapping schemas should be avoided anyway and with linting on process level, this might not become a problem. I propose to go with the simple solution now and fix it when users notice it

[philippfromme]

@marstamm walked me through it and I verified it works as expected. Approval from my side. ✅