Provide visual tooling for building common layout patterns

## Problem
It's easy to run into errors or unintended results when building layouts from scratch. For example, building a ListTile-like layout from Row and Column can often lead to the RenderFlex overflow error.

## Proposal
The IDE can help the user avoid layout errors by providing code snippets for building common layout patterns. We could potentially use [Live Templates](https://www.jetbrains.com/help/idea/using-live-templates.html) for this purpose as a starting point. But it would be even better if the available layout templates are visually represented in a catalog. Here is an example: https://docs.dhtmlx.com/layout__patterns.html.

This feature would be a natural extension of the existing "Wrap in a Column/Row" workflow and the proposed integrated widget catalog feature (#4081).