Property Editors: Added form control and mandatory support(User, Member, Member Group)

[engijlr]

Summary

Update some Property Editors to align with the FormControl validation pattern.

Changes

• Extended each component with UmbFormControlMixin.
• Bound the inner input element to the form control (addFormControlElement).
• Added support for mandatory and mandatoryMessage properties.
• Ensured that if a field is not mandatory, it supports undefined values.
• Added a value-missing validator inside the inner input for proper required-state validation.
• Implemented consistent handling for required, requiredMessage, and readonly.
• Fixed small typos and attribute mismatches across components.