RSLabel wrongly reports width with italics, breaks RSComposite

[JanBliznicenko]

RSLabel reports the same width for both normal and italics, although text in italic is wider. If the label is then placed in a RSComposite, it crops part of the text or, if italics text is changed back to normal, it leaves part of previous render there.

Example that produces the result in the screenshot:

canvas := RSCanvas new.
canvas @ RSDraggableCanvasInteraction @ RSZoomableCanvasInteraction.
canvas camera scale: 4.

labelW := RSLabel new.
labelW text: 'W'.
labelW italic.
compositeW := RSComposite new.
compositeW add: labelW.
canvas add: compositeW.

labelM := RSLabel new.
labelM text: 'M'.
labelM italic.
compositeM := RSComposite new.
compositeM add: labelM.
compositeM translateBy: 0@20.
canvas add: compositeM.

canvas open.
[50 milliseconds wait.
labelM normal.
labelM signalUpdate.] forkAt: Processor userBackgroundPriority 

Possible unit test:

| label normalWidth italicWidth |
label := RSLabel new.
label text: 'M'.
normalWidth := label width.
label italic.
italicWidth := label width.
self assert: italicWidth > (normalWidth + 0.001)