[Web] Use the module config to preload GDExtension libraries.

Instead of calling loadDynamicLibraries ourselves, we add the
GDExtension libraries to preload to the "dynamicLibraries" module config
property.

This seems to fix some threading issue with some browsers during the
init phase.

platform/web/js/engine/config.js

@@ -271,12 +271,13 @@ const InternalConfig = function (initConfig) { // eslint-disable-line no-unused-
 	 */
 	Config.prototype.getModuleConfig = function (loadPath, response) {
 		let r = response;
+		const gdext = this.gdextensionLibs;
 		return {
 			'print': this.onPrint,
 			'printErr': this.onPrintError,
 			'thisProgram': this.executable,
 			'noExitRuntime': false,
-			'dynamicLibraries': [`${loadPath}.side.wasm`],
+			'dynamicLibraries': [`${loadPath}.side.wasm`].concat(this.gdextensionLibs),
 			'instantiateWasm': function (imports, onSuccess) {
 				function done(result) {
 					onSuccess(result['instance'], result['module']);
@@ -300,6 +301,8 @@ const InternalConfig = function (initConfig) { // eslint-disable-line no-unused-
 					return `${loadPath}.audio.worklet.js`;
 				} else if (path.endsWith('.js')) {
 					return `${loadPath}.js`;
+				} else if (path in gdext) {
+					return path;
 				} else if (path.endsWith('.side.wasm')) {
 					return `${loadPath}.side.wasm`;
 				} else if (path.endsWith('.wasm')) {

platform/web/js/engine/engine.js

@@ -163,19 +163,14 @@ const Engine = (function () {
 					me.rtenv['initConfig'](config);
 
 					// Preload GDExtension libraries.
-					const libs = [];
 					if (me.config.gdextensionLibs.length > 0 && !me.rtenv['loadDynamicLibrary']) {
 						return Promise.reject(new Error('GDExtension libraries are not supported by this engine version. '
 							+ 'Enable "Extensions Support" for your export preset and/or build your custom template with "dlink_enabled=yes".'));
 					}
-					me.config.gdextensionLibs.forEach(function (lib) {
-						libs.push(me.rtenv['loadDynamicLibrary'](lib, { 'loadAsync': true }));
-					});
-					return Promise.all(libs).then(function () {
 					return new Promise(function (resolve, reject) {
-							preloader.preloadedFiles.forEach(function (file) {
+						for (const file of preloader.preloadedFiles) {
 							me.rtenv['copyToFS'](file.path, file.buffer);
-							});
+						}
 						preloader.preloadedFiles.length = 0; // Clear memory
 						me.rtenv['callMain'](me.config.args);
 						initPromise = null;
@@ -183,7 +178,6 @@ const Engine = (function () {
 						resolve();
 					});
 				});
-				});
 			},
 
 			/**