Make it possible for asset libraries to return more than one core library

libraries.module

src/ExternalLibrary/Asset/AssetLibrary.php

src/ExternalLibrary/Asset/AssetLibraryInterface.php

src/ExternalLibrary/Asset/SingleAssetLibraryTrait.php

...alLibrary/Exception/InvalidLibraryDependencyException.php

...ternalLibrary/Exception/LibraryClassNotFoundException.php

...lLibrary/Exception/LibraryDefinitionNotFoundException.php

src/ExternalLibrary/Utility/DependencyAccessorTrait.php

src/ExternalLibrary/Utility/LibraryAccessorTrait.php

src/ExternalLibrary/Utility/LibraryIdAccessorTrait.php