Add Grafana and Metabase tutorials from Cloud Docs

[amotl]

About

There are only two spots where integration tutorials have been added to the Cloud Docs. This patch intends to integrate them here in a canonical way instead, to set the stage for adding more like those, and to get them out of the way when further refactoring Cloud Docs in the course of the next iterations over there.

Personally, I don't care too much whether the content is biased towards CrateDB Cloud or not. Adjustments to this detail, to better balance between cloud vs. self-managed, can always be made on behalf of subsequent iterations.

Preview

• https://crate-clients-tools--37.org.readthedocs.build/en/37/visualize.html
• https://crate-clients-tools--37.org.readthedocs.build/en/37/integrate/grafana.html
• https://crate-clients-tools--37.org.readthedocs.build/en/37/integrate/metabase.html

Previous

Those are the current/previous resources.

• https://crate.io/docs/cloud/en/latest/howtos/visualize-data-with-grafana.html
• https://crate.io/docs/cloud/en/latest/tutorials/integrations/metabase.html

[mergify[bot]]

:warning: The sha of the head commit of this PR conflicts with #39. Mergify cannot evaluate rules on this PR. :warning: