Obsolete GC operations in history

[HeikoKlare]

The GC stores every operation changing the GC state to be able to repply it if a handle for a different zoom is requested. There are some operations which, if executing an operation of the same type subsequently, supercede each other. This, for example, applies to setting fonts, as when settings two fonts after each other, only the last one set is relevant. This was the reason for adapting the GC in Draw2d's FigureUtilities. That, however, introduced multiple issues, including (but not limited to) reduced testability of memory leaks in diagrams as the statically stores but frequently replaced GCs will be detected as memory leaks.

The proposed change allows to revert the changes to FigureUtilites as it resolves the memory leak already in SWT/GC.

Tracking ticket for:

• [Win32] Remove superceded GC operations from history eclipse-platform/eclipse.platform.swt#2689