Component groups for code components

Overview

Placeholder — needs issue summary update

Users need to be able to add code components to groups. Other components (sourced from SDCs and blocks) already have a category defined for this purpose (see #3459088: Every XB `Component` config entity should have a `category` property) — the terminology should be made consistent, i.e. group vs. category —, but the UI doesn't make use of them yet.

With code component groups, we need to answer the following questions:

1. Do we allow adding a code component to a group which is defined by an SDC or a block?
2. How do we store groups created specifically for code components?
3. How does the UI look like for managing these groups? Creating new ones could be done when adding a new component, but how can we edit or delete existing ones?
4. What are the available groups when adding a code component to components (done in #3500071: Adding code components to components)?

Proposed resolution

TBD

User interface changes