Universal class for all type of embedding models

[generall]

It looks like currently we have different base classes for Jina and all the other embedding models.
That creates confusing user experience and in general over-complicates usage (see tests, for example).

We need to implement a single common class for all dense text models, which should internally route to the proper internal implementaiton.

[joein]

+1

We already have problem with using JinaEmbedding within qdrant-client integration, there is just no interface to choose it