Optimize SVG icons and remove unused Transpose icon

[MewPurPur]

Moar! The icons folder is now less than 100π kilobytes, reducing the executable size by 10 kB. A few icons were tweaked, having their small artifacts and imprecision fixed up. Most importantly the CPUParticles gizmo, which wasn't synced with how I recently simplified the overly detailed icon, was tweaked.

The transpose icon used to show up in the 3.x tilemap editor, now it's unused. I think the icon was so unclear that if we need something like it again, we might as well re-do it.

[capnm]

@MewPurPur I can't believe it, on the tip d28f9af it's complaining during a clean startup with only 3 tiny details. Fixing that could make it yet smaller and faster :)

This seems to be coming from the platform/macos/export/run_icon.svg
[L] SVG (thirdparty/thorvg/src/loaders/svg/tvgXmlParser.cpp 523): 
Unsupported attributes used [Elements type: Path][Id : NO_ID][Attribute: -inkscape-stroke][Value: none]

[L] GD (./editor/editor_themes.cpp:249) editor_generate_icon: 
	--> Loading icon[157] CopyNodePath.svg
[L] SVG (thirdparty/thorvg/src/loaders/svg/tvgSvgLoader.cpp 3213): 
Inefficient elements used [Size is zero][Node Type : Circle]

[L] GD (./editor/editor_themes.cpp:249) editor_generate_icon: 
	--> Loading icon[314] GuiSpinboxUpdownDisabled.svg
[L] SVG (thirdparty/thorvg/src/loaders/svg/tvgXmlParser.cpp 363): 
Unsupported attributes used [Elements type: Svg][Id : NO_ID][Attribute: enable-background][Value: new 0 0 16 16]

[MewPurPur]

Okay! Fixed all three.

[YuriSizov]

Thanks!