FeathersTextInput needs manually placing in a FeathersTextInputContainer unlike other controls

## What problem does this solve or what need does it fill?

Currently to setup a feathers text input you need to do:

```
@FeathersTextInputContainer Children [
MarkerTestValueString
@FeathersTextInput {

}
...
]
```

Which is different to other controls which contain all their decoration.

## What solution would you like?

The current way has been done deliberately in case you want to embed other controls inside the container but outside the text input. This same thing could be achieved with an extra properties or similar...

```
@FeathersTextInput {
@extra_controls: bsn! { ... }
}
...
```

## Alternative

An alternative could be that you have a "bare" property on FeathersTextInput that displays it bare so you can place it as currently, but by default it contains its container. I like that just as much.

The issue names FeathersTextInput and FeathersTextInputContainer but no files or tests. Start by locating those controls and comparing how other controls include their decoration. Clarify whether default containment or a bare/extra-controls option is intended, then add coverage showing the chosen behavior.

Written by the indexing model from the issue text.