Change bundlesize reporter to use brotli size

[jridgewell]

The gzip file size is largely irrelevant now, and certain optimizations we make that reduce the size of the gzip output can actually increase the size of the brotli output.

[rsimha]

Switching the calculation should be fairly straightforward by adding -c brotli to the npx bundlesize invocation.

amphtml/build-system/tasks/bundle-size.js

Lines 46 to 63 in 8833970

	/**
	* Get the gzipped bundle size of the current build.
	*
	* @return {string} the bundle size in KB rounded to 2 decimal points.
	*/
	function getGzippedBundleSize() {
	const cmd = `npx bundlesize -f "${runtimeFile}"`;
	log('Running', cyan(cmd) + '...');
	const output = getStdout(cmd).trim();
	const bundleSizeOutputMatches = output.match(/PASS .*: (\d+.?\d*KB) .*/);
	if (bundleSizeOutputMatches) {
	const bundleSize = parseFloat(bundleSizeOutputMatches[1]);
	log('Bundle size is', cyan(`${bundleSize}KB`));
	return bundleSize;
	}
	throw Error('could not infer bundle size from output.');
	}

However, there will be a period when PRs will have base commits for which we only have the gzipped bundle size. I suppose we can ease into this by initially computing both sizes, and then switching exclusively from gzip to brotli at some point.

Assigning to @danielrozenberg.

[danielrozenberg]

My work plan on changing this is as follows:

1. Modify the reporter for push builds to double-write the bundle size on each commit to bundle-size/[SHA] (gzip) and bundle-size/[SHA].br (brotli), do this for 1 month
2. 1. Modify the reporter for pull requests to report both gzip and brotli bundle-sizes to the app
   2. Modify the bundle-size app to read the [SHA].br instead of the [SHA] file
3. 1. Stop reporting the gzip size for pull-requests and push-builds
   2. Delete all gzip sizes in amphtml-build-artifacts
   3. Cleanup any leftover gzip code

[rsimha]

Reverted in #24882

[danielrozenberg]

Unreverted in #24888