Fix missing element dimensions

[vadimdemedes]

Fixes #557.

The root cause of the issue was that both layout calculation and rendering of output was in the same onRender function that's throttled to 32ms by default:

ink/src/ink.tsx

Lines 53 to 58 in 025c10f

	this.rootNode.onRender = options.debug
	? this.onRender
	: throttle(this.onRender, 32, {
	leading: true,
	trailing: true
	});

And here's the function that would be called:

ink/src/renderer.ts

Lines 16 to 23 in 025c10f

	node.yogaNode.calculateLayout(undefined, undefined, Yoga.DIRECTION_LTR);
	const output = new Output({
	width: node.yogaNode.getComputedWidth(),
	height: node.yogaNode.getComputedHeight()
	});
	renderNodeToOutput(node, output, {skipStaticElements: true});

So when component is mounted/unmounted frequently, as in the original issue, and it calls measureElement in a useEffect, there's a condition when useEffect is executed before Yoga layout is calculated. This leads to NaN being returned instead of element dimensions.

This PR fixes that by separating code that calculates layout and renders output to the terminal. Calculation of layout is now always instant, while output rendering continues to be throttled.