Fix: reset default values for usergroup column after row creation

[Koc]

Reproducer

1. Create a table with usergroup columns (single and multi-selection)
2. Open modal for add new row
3. Toggle on "add more"
4. Create a row

Expected result

all columns were reset after row creation.

Actual result

usergroup columns weren't reset

🖼️ Screenshots

before	after

Also it makes usergroup component more consistent with with SelectionForm and SelectionMultiForm component (use same approach with computed mutable property)