Cleanup jest config (#2959)

Some small cleanups with regards to jest
- call jest directly (nyc is integrated in jest these days)
- move jest config into seperate file so we dont clutter up the
package.json
- remove empty test file for newsletter-unit-tests
- update dependencies that touch jest
- try out v8 as coverageProvider

Co-authored-by: veeck <michael@veeck.de>

tests/unit/functions/newsfeed_spec.js

@@ -1,15 +0,0 @@
-describe("Functions into modules/default/newsfeed/newsfeed.js", () => {
-	// Fake for use by newsletter.js
-	Module = {};
-	Module.definitions = {};
-	Module.register = (name, moduleDefinition) => {
-		Module.definitions[name] = moduleDefinition;
-	};
-
-	beforeAll(() => {
-		// load newsfeed.js
-		require("../../../modules/default/newsfeed/newsfeed.js");
-	});
-
-	test.skip("skip", () => {});
-});