Missing functionalities for artefact store

[jasonjunweilyu]

Currently, artefacts.py does not explicitly have methods for creating a new collection and filtering collections with filenames. So this additional method is needed for class ArtefactStore:

def filter_create_new(self, existing_collection: Optional [Union[str, ArtefactSet]], filenames: Optional[Union[Path, str, Iterable[Path], Iterable[str]]], new_collection: str):

This would enable the users to

(1) specify the files they want with filenames, filter an existing collection with the filenames and then return a new collection that is a subset of the existing collection.
(2) create an empty collection if the optional arguments are not set.

User cases of this would be like pass a collection to sourcegetter of a new psyclone step.

[hiker]

Migrated to MetOffice#356