Change forceUpdate flag to always force recalculation of width. Fix tests. (#13444)

Change-Id: Ie666e2867908160b1544d3bf8251802ea771660f

Conflicts:
	client/src/com/vaadin/client/ui/VFilterSelect.java
	uitest/src/com/vaadin/tests/components/ui/ComboboxStyleChangeWidthTest.java
Treat initial rendering and style changes separately. (#13444)

This fixes a regression caused by a previous patch, which led to empty comboboxes being initialised with a zero width.

Change-Id: I7e5ca0c563625c453e0e3006d91ed52ad227d6f0

Conflicts:
	client/src/com/vaadin/client/ui/combobox/ComboBoxConnector.java
Move ComboBox tests to correct package

Change-Id: I2ad5164a637b2b4c96b46f30df036ccbc5cbcd66

Conflicts:
	uitest/src/com/vaadin/tests/components/combobox/ComboboxStyleChangeWidth.java
	uitest/src/com/vaadin/tests/components/combobox/ComboboxStyleChangeWidthTest.java