`unnecassary_stack`, `unnecassary_row`, and `unnecassary_column`

[Number-3434]

Lint that informs when a Stack, Row, or Column only has a single child in the children parameter.

// BAD, has only one child in children
const Stack(children: [Text('Hello World!')]),
const Row(children: [Text('Hello World!')]),
const Column(children: [Text('Hello World!')]),

// GOOD, has more than one child in children
const Stack(children: [Text('Hello World!'), Text('Hello World Again!')]),
const Row(children: [Text('Hello World!'), Text('Hello World Again!')]),
const Column(children: [Text('Hello World!'), Text('Hello World Again!')]),

[pq]

@goderbauer

[goderbauer]

This would be sort of similar to the avoid_unnecessary_containers. I wouldn't be opposed to this lint existing, but I also wonder how much value it would bring. Would be interesting to see how many unnecessary widgets of those types exist in a larger code base. Unlike unnecessary containers I haven't seen many (any?) of these cases in code reviews.