* experimental: support connection strings for databases using connectorx
This adds an experimental support for connector strings using connectorx.
User has to provide config for the connection strings with:
Example:
```console
dvc config --local db_connection.pg postgres://user:pass@localhost:5432/database
```
And then, they can import using:
```console
dvc import-db --sql 'query' --conn pg
```
Check supported databases and how to configure in https://sfu-db.github.io/connector-x/databases.html.
This `db_connection` config is subject to change.
connectorx still has the same problem with dbt as before: no support for streaming,
but it'll be a bit more simpler to configure with the connection strings.
* add pandas to deps
* sqlalchemy
* dbt streaming sql
* fix test
* remove connectorx
* remove check in set
* use mode='wb' for serialization
skshetry