Make product analytics visualization designer Snowplow-compatible

What does this MR do and why?

Updates the Visualization Designer to be Snowplow compatible by ensuring the correct fields of the snowplow schema are referenced.

Also updated mocked data to match the latest schema.

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. Follow these instructions to set up Product Analytics in your GDK.
2. Enable the Snowplow flag by running the command: echo "Feature.enable(:product_analytics_snowplow_support)" | rails c.
3. Enable the dashboard editor flag by running the command: echo "Feature.enable(:combined_analytics_dashboards_editor)" | rails c.
4. Set up a new project and onboard it with Snowplow via Project → Analytics → Dashboards.
5. Track some events and page views for the project via the SDK.
6. Visit the visualization designer at Project → Analytics → Dashboards -> Visualization Designer and verify you can browse data and create visualizations.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #408095 (closed)