fix: memory leak in folder configuration

[SimonSiefke]

Fixes some memory leaks in folder configuration / configuration service.

Issue one: Registering to global configuration service

Since there is only one global configuration service, registering a folder configuration to that class using this._register makes it so the class holds on to the folder configuration forever, since the global configuration service is never disposed.

private loadFolderConfigurations(folders: IWorkspaceFolder[]): Promise<ConfigurationModel[]> {
	/* ...*/
	let folderConfiguration = this.cachedFolderConfigs.get(folder.uri);
	if (!folderConfiguration) {
		folderConfiguration = new FolderConfiguration(!this.initialized, folder, FOLDER_CONFIG_FOLDER_NAME, this.getWorkbenchState(), this.isWorkspaceTrusted, this.fileService, this.uriIdentityService, this.logService, this.configurationCache);
		this._register(folderConfiguration.onDidChange(() => this.onWorkspaceFolderConfigurationChanged(folder)));
		this.cachedFolderConfigs.set(folder.uri, this._register(folderConfiguration));
	}
	return folderConfiguration.loadConfiguration();
})]);
}

Fix

Registering all folder related disposables only to the map cachedFolderConfigs: Map<URI, FolderConfiguration>

Issue two: Resetting caches

This code resets the caches, but it doesn't dispose the values of the map.

// reset caches
this.cachedFolderConfigs = new ResourceMap<FolderConfiguration>();

Fix

Switching to a DisposableMap and making use of it's clearAndDisposeAll function.

Before

When executing a task 97 times, the number of functions/objects related to FolderConfiguration grows each time

After

When executing a task 97 times, while the number of various functions/objects still grows, it seems there are no more leaks related to FolderConfiguration

[SimonSiefke]

(updated branch to try to fix MacOS CI timeout)