Allow vanilla qdrant filters

[jdb78]

Allow passing a qdrant filter object instead of a haystack filter object - this is useful when the haystack filter object does not support the use case, e.g. when to use full text search and when to match exactly

[CLAassistant]

All committers have signed the CLA.

[silvanocerza]

I'm a bit unsure about this change to be fair.

I understand the need obviously, though we'd need to change also the filter_documents() signature to reflect this. The retrievers too I guess. It's not enough to change the conversion function.

I'm not sure whether linting would be happy though, changing the signature like this might mean breaking the Document Store Protocol for some linters probably. 🤔

I would probably do this only for the retrievers as most of the times they don't use filter_documents() directly to retriever documents.

[jdb78]

updated the signatures