Unify schemas and datasets across the docs

## Why are we implementing it? (sales eng)

As the docs have evolved, different sections use schemas from different topics, like wikipedia edits, github events, ad analytics, IoT sensors. Does it make sense to cut down on these and share more between the pages of the docs?

### What are the typical use cases?

## Communication goals (e.g. detailed howto vs orientation)

### Good locations for content in docs structure

## How does this work? (devs)

### Example sql

### Corner cases, gotchas

### Are there relevant blog posts or outside documentation about the concept/feature?

### Link to relevant commits and regression tests if applicable