ObservableObject setters should check for equality before assigning

[GeertvanHorrik]

Instead of this:

        public string ExistingProperty
        {
            get => _existingProperty;
            set
            {
                _existingProperty = value;
                RaisePropertyChanged(nameof(ExistingProperty));
            }
        }

into:

        public string ExistingProperty
        {
            get => _existingProperty;
            set
            {
                if (_existingProperty == value)
                {
                    return;
                }

                _existingProperty = value;
                RaisePropertyChanged(nameof(ExistingProperty));
            }
        }

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