This PR updates Qdrant to 1.1.1 and introduces local mode, so there is
no need to spin up the Qdrant server. By that occasion, the Qdrant
example notebooks also got updated, covering more cases and answering
some commonly asked questions. All the Qdrant's integration tests were
switched to local mode, so no Docker container is required to launch
them.
`persist()` is required even if it's invoked in a script.
Without this, an error is thrown:
```
chromadb.errors.NoIndexException: Index is not initialized
```
