Improve the discovery of the pipelines registry dropdown in Kedro-Viz

[stephkaiser]

Description

We've heard from multiple users that they didn't notice the pipeline registry dropdown in the top left of Kedro-Viz.

"All my pipelines are summed into one default in the registry - I simply did not see the pipeline dropdown in the top-left. I selected default and it shows all."

https://kedro.hall.community/kedro-viz-only-shows-one-node-from-multiple-pipelines-33p5kGrMKkXW#5d491dec-7fc9-46db-82a4-118d31a5d4b6

Possible Implementation

• Is the default pipeline (showing all pipelines) on by default?
• Should we highlight this feature in an onboarding experience when users first open Kedro-Viz?
• Could be possibly make the dropdown more noticeable without changing too much in Kedro-Viz?