Pick a custom emoji for an Entity (imitate single-select)

Description

Problem

While Views and select options have icons, regular Entities don't have any. This limits the customization opportunities and produces a less sexy UI when Entities are used in place of selects and Docs:

Tag-like DBs, possible shared between multiple related DBs:
- Niche
- Segment
- Category
- State (ex. shared across Stories and Bugs)
Entity-based wiki where some extra Fields are needed (ex. Maintainer, Status)

Currently, we have to add emojis into Entities' names:

This produces a messier UI and makes export and auto-linking challenging.

Solution

?entity-icons

Create new Icon Field
1. ❓ might be the current Emoji Field but with some flag indicating it's a primary one
Pick an icon for an Entity
1. on Entity View
2. in emoji unit
3. 🦄 elsewhere

This would be useful for Display a to-many relation as compact list on Entity View: think emojis for Teams/Segments/Tags.

Places

Entity View header
Emoji unit
- table and grid views
- other views (update old emoji unit to make it editable)
- 🦄 whiteboard
Left menu
- Smart Folder
- Favourites
- ☝️ If DB has both Avatar and Icon extensions, always show Avatars
Search
- in place of DB abbreviation badge
- 🦄 show Avatar in place of DB abbreviation badge
  (Avatar > Icon if both are present)
To-one and to-many relation unit instead of triangles
- Entity View
- Unit (pinned Fields, Views)
Mention
- always show instead of abbreviation badge
  (remember about …)
Share Space with Groups
(Avatar > Icon if both are present on the same DB)
- Admins 👑
- Everyone 🧢

Notes

We already have an Emoji Field (hold alt when creating a new Field) and it's nicely displayed on some Views:
Preserve Document's icon when converted to Entity if Icon Field is present on the Entity's DB
Check
- Entity sharing
- Export-import via Space templates

Out of scope

Pick color
🦄 Picking an icon and color via an automation/Formula
- Country.Icon = ":flag" + [Country Code] + ":"
- 🦄🦄🦄 Color
  - Country.Color = Region.Color
  - Project.Color = Objective.Color
  - Story.Color = Team.Color