Replace jsReady.js and moduleReady.js with waitForNetworkIdle call

jsReady.js and moduleReady.js effectively wait for various JS resource loader
modules to load which can be tedious to write and error prone. There might be a
better and more future-proof alternative by waiting for the network to idle
instead.

Therefore, this commit:

* Replaces all usages of waitForModule with waitForNetworkIdle
* Removes moduleReady.js and jsReady.js

Bug: T322454

Author: Nicholas Ray

src/engine-scripts/puppet/echo.js

@@ -1,5 +1,3 @@
-const moduleReady = require( './moduleReady' );
-
 /**
  * Setup Echo notifications
  *
@@ -15,15 +13,12 @@ module.exports = async ( page, hashtags ) => {
 
 	// Open the drawer for tests that require interaction
 	if ( hashtags.includes( '#echo-drawer' ) ) {
-		await moduleReady( page, 'ext.echo.init' );
 		await page.evaluate( async () => {
 			const btn = document.querySelector( '#pt-notifications-alert a' );
 			btn.click();
 		} );
-		await moduleReady(
-			page,
-			hashtags.includes( '#mobile' ) ? 'ext.echo.mobile' : 'ext.echo.ui.desktop'
-		);
+		// Wait for JS to load.
+		await page.waitForNetworkIdle();
 
 		// Wait for the OOUI pending element to disappear.
 		await page.waitForSelector( '.oo-ui-pendingElement-pending', {

src/engine-scripts/puppet/jsReady.js

@@ -12,8 +12,8 @@ module.exports = async ( page, scenario ) => {
 	const label = scenario.label;
 	const hashtags = label.match( /(#[^ ,)]*)/g ) || [];
 
-	// Make sure the main skin JavaScript module has loaded.
-	await require( './jsReady' )( page, hashtags );
+	// Wait for async js to finish loading.
+	await page.waitForNetworkIdle();
 
 	if ( hashtags.includes( '#scroll' ) ) {
 		await require( './scroll.js' )( page );

src/engine-scripts/puppet/moduleReady.js

@@ -1,4 +1,3 @@
-const moduleReady = require( './moduleReady' );
 const fastForwardAnimations = require( './fastForwardAnimations' );
 
 /**
@@ -49,8 +48,9 @@ module.exports = async ( page, hashtags ) => {
 	} else {
 		// Make sure Codex kicked in.
 		await page.waitForSelector( '.cdx-typeahead-search' );
-		// Wait for Vue to load.
-		await moduleReady( page, 'vue' );
+		// Wait for JS to load.
+		await page.waitForNetworkIdle();
+
 		// focus and type into the newly added input
 		await page.focus( selectorSearchInput );
 		await page.keyboard.type( 't' );