Match tag styles on meeting and orga level

[Elblinator]

Currently:
The appearance from the tags on the Orga-level and the meeting-level differ:

Tags-list on Orga-level:

Orga Tags on something (here a committee):

Tags-list on Meeting-level:

Meeting Tags on something (here a motion):

Wanted:
The Tags on the Orga level and the meeting level should be displayed in the same manner
Backend:

• Match tag styles on meeting and orga level openslides-backend#2381
• first/waiting for: changes in backend: additional field colour, and the ability to set it using tag.update and -create
• for already created tags I would recommend setting the colour to the accent colour

Client:

• The client needs to allow to create/update tags with colour
• The client needs to display the tags with the same outline and according colour as the orga-tags

[luisa-beerboom]

As I also said in the backend PR This would cause the two models to be functionally the same in meeting and orga, with the exception of the meeting_id/organization_id properties, what do we think about unifying them into one model, paving the way for new features like globally available tags and giving the developers the ability to add new features to both at the same time?

[Elblinator]

I like the idea of unifying them

[Elblinator]

If this Issue is fixed then the following should also be fixed:
#2935