Domain groups table: Implement custom multiselect component for creating and editing domains

[zandercymatics]

Issue description

Domain groups are meant to act like a label on a domain. These will be set by admin users to "group" domains together to help with their own internal organization. For instance, some users may group domains that have a particular manager or who expire within the same month. Just like in github where we can filter by a label, the goal is to let users filter by any set of domain groups (labels).

In #2433, we added add/edit functionality for domains. This PR included a simplified approach towards adding them. However, a custom multiselect component is desired for this functionality which will be the purpose of ticket.

Acceptance criteria

• [ ] The old components for adding domains in the create and edit modes are replaced with the multiselect specified in the figma
• [ ] Implementation conforms to specifications in the figma

Additional context

Note: We already have a multiselect component called django-select2 in Django admin. It may be possible to reuse this component if so desired (though not required). More specifically, select2 has multiple select support in the form of a pillbox.

Links to other issues

⛔ Blocked by:

• 2396

• https://github.com/cisagov/manage.get.gov/issues/2435

• 2433

🔄 Relates to:

• 2434

[PaulKuykendall]

@zandercymatics - when you're finished creating this, we can remove the refinement tag