Fix CTabFolder Trim Calculation logic

[amartya4256]

Description
The CTabFolder trim is calculated using some magic numbers represented in points which can have adverse effect when scaled to pixels. Hence, it should be calculated in pixels and then converted into points using OfFloat variants to preserve inversibility.

TODO: needs more details

[akoch-yatta]

@amartya4256 What is the state of this? probably still necessary, isn't it? If yes, fill the TODO please 😄

[amartya4256]

Let's wait for the Point. OfFloat fix from eclipse-platform/eclipse.platform.swt#2502, since it seems indirectly related. The trim is needed to compute size and the trim is represented in Point (as size), which might be fixed using the Point.OfFloat.asSize() and Point.OfFloat.asLocation() variants. I'll add it in the description.