optimize Folder::getById to use less queries

lib/private/Files/Config/CachedMountInfo.php

lib/private/Files/Config/LazyStorageMountInfo.php

lib/private/Files/Config/UserMountCache.php

lib/private/Files/Node/Folder.php

lib/private/Files/Node/Root.php

lib/private/Server.php

lib/public/Files/Config/ICachedMountInfo.php

tests/lib/Files/Config/UserMountCacheTest.php

tests/lib/Files/Node/FileTest.php

tests/lib/Files/Node/FolderTest.php

tests/lib/Files/Node/HookConnectorTest.php

tests/lib/Files/Node/IntegrationTest.php

tests/lib/Files/Node/NodeTest.php

tests/lib/Files/Node/RootTest.php