Editor GPU: Consider changing the strategy for allocating glyphs into slabs

[Tyriar]

Slabs right now are reserved for glyphs of the exact width and height of the slab. This could be wasteful and will likely just be more so as the device pixel ratio increases. We should consider using a different strategy as called out here:

vscode/src/vs/editor/browser/gpu/atlas/textureAtlasSlabAllocator.ts

Lines 98 to 120 in bd21f3c

	// TODO: Include font size as well as DPR in nearestXPixels calculation
	// Round slab glyph dimensions to the nearest x pixels, where x scaled with device pixel ratio
	// const nearestXPixels = Math.max(1, Math.floor(dpr / 0.5));
	// const nearestXPixels = Math.max(1, Math.floor(dpr));
	const desiredSlabSize = {
	// Nearest square number
	// TODO: This can probably be optimized
	// w: 1 << Math.ceil(Math.sqrt(glyphWidth)),
	// h: 1 << Math.ceil(Math.sqrt(glyphHeight)),
	// Nearest x px
	// w: Math.ceil(glyphWidth / nearestXPixels) * nearestXPixels,
	// h: Math.ceil(glyphHeight / nearestXPixels) * nearestXPixels,
	// Round odd numbers up
	// w: glyphWidth % 0 === 1 ? glyphWidth + 1 : glyphWidth,
	// h: glyphHeight % 0 === 1 ? glyphHeight + 1 : glyphHeight,
	// Exact number only
	w: glyphWidth,
	h: glyphHeight,
	};