Wildcard: Add first implementation of `<MultiCombobox />` component

Created by: vovakulikov

Background

A few code insights pages already have something like the Combobox component but instead of Combobox, they use something similar. A good example of it can be search-based insight creation UI (the repositories field).

Code insights creation UI search repositories field

This field uses just a simple input with some logic on top of it. This logic is complex and sometimes when you work with simple text to manage a few items in this field (a few repositories) it can be complicated for users and can lead to some bugs there.

Also, Multibox would be useful for further change in the creation UI form when we start implementation of the new dashboards settings section in the form.

This PR adds the MultiCombobox component but doesn't add this to the creation UI. It will be done in a separate PR.

Light theme	Dark theme

Work in progress but not blockers for design review

1. A11y support (labels, focus management)
2. Overflow content checks