Singlestoredb

* Add pytest plugin

* Fix deferred connection URL in HTTP

* Change Stage URLs
* Fix password encoding in deferred connections

* Make workspace group optional in Fusion SQL if it is specified in the environment

* Cache regions in Management API
* Add dummy fields to Region objects if the region ID does not point to an existing region

* Add JWT authentication support to Fusion
* Add experimental vector data format support to UDF server
* Rename `stages` to `stage`
* Add `track_env` connection parameter to automatically track the `SINGLESTOREDB_URL`
environment variable