fix: UIKit VitaminButton and VitaminTextField minor fixes

Changes description

Minor fixes on UIKit VitaminButton :

Minor fixes on UIKit VitalinTextField

text field can now be instantiated programmatically (it crashes in current version)
background color is now transparent
top constraint was not set properly, causing field to be shifted upward
height is now computed (with overriding intrinsicContentSize), height constraint is not mandatory anymore
helper text can be displayed on many lines

This changes are fixes from integrators feedbacks (Domyos eConnected, and Connected Locker)

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