Set up workflow for e2e nightly runs with preliminary set of tests

[julian-risch]

Get the outdated e2e tests running with just one quick test, nightly just as the nightly tutorial runs: https://github.com/deepset-ai/haystack-tutorials/blob/974aee41fc464cf3d7ccc76eb16f52e40462b242/.github/workflows/nightly.yml#L5

• Tests in e2e/document_stores/test_update_embeddings.py can be converted into multiple unit tests without real documentstores or retrievers
• Tests in e2e/document_stores/test_cosine_similarity.py can be converted into integration tests. They are testing that all doc stores behave in the same way.
• Tests in e2e/document_stores/test_similarity_score.py look like end-to-end tests but some of them could be merged, not testing all parameter combinations separately