deps: update to typescript 4.7

[brendankenny]

typescript 4.6 and typescript 4.7 have been released since we last updated, so it seemed time to update.

Unlike most updates, we only had a single new error that we needed to fix, and there's nothing new that our code could really benefit from, so it's a pretty simple update. There are some nice updates in typescript 4.6 that people may want to take advantage of (like still being able to discriminate between objects in a union even after the objects are destructured), and typescript 4.7 should make us more resilient in the future if more dependencies start doing complicated package.json exports.

We can wait to land this for typescript-eslint to officially support 4.7 so we don't get the version warning in yarn lint, but that should be today or tomorrow.

[brendankenny]

this was the only new "error". new Intl.DisplayNames().of() can return undefined, and optionEl.textContent is supposed to only take string|null, so that was the incompatibility.

In reality, I believe new Intl.DisplayNames only returns null if fallback: 'none' is set, otherwise it always falls back to locale, so this fallback is mostly for tsc's sake, and just in case I'm reading the spec wrong.

[brendankenny]

I was looking at the outDirs in all the tsconfigs recently and was kind of annoyed, but it turns out if I had just looked at the rootDir docs I would have realized it only affects emit, not includes, excludes, etc, so specifying this once in the base tsconfig works perfectly. Makes the extending tsconfigs much nicer, and should fix your problem in c55da8b, @connorjclark

[brendankenny]

checking the diff on the outDir also revealed a minor bug here: this one was saving one directory too high. Check the parent directory of your lighthouse repo and there will be a .tmp in there, too. Sorry :)

[connorjclark]

nit: i'm recently of the opinion that leading ./ in paths are pointless noise. if a path is not starting with / I know it is relative :)

[brendankenny]

I don't really care, it just bothers me that rootDir: '' isn't the identity instead of '.' in this case, since they're right next to each other :)

[brendankenny]

I also took a second look at this workaround for the flow report:

lighthouse/build/build-report.js

Lines 72 to 80 in 94b4f38

	rollupPlugins.typescript({
	tsconfig: 'flow-report/tsconfig.json',
	// Plugin struggles with custom outDir, so revert it from tsconfig value
	// as well as any options that require an outDir is set.
	outDir: null,
	composite: false,
	emitDeclarationOnly: false,
	declarationMap: false,
	}),

with the latest version of @rollup/plugin-typescript, you can get away with removing the outDir and emitDeclarationOnly overrides there, but only if you've already run yarn type-check so everything is already cached in .tmp/tsbuildinfo, so it's probably not worth it. If ui-strings.js and localized-strings.js were typescript files it might work, but it seems to not handle having these js files in the output when it's a composite compile.

To really fix it we probably just need it to get closer to a real build tsconfig, and having those emitDeclarationOnly for js files in there is kind of confusing. Alternatively we could just build it ourselves to a tmp directory and run rollup on the output there.