`FloatingPanel` - Content without container is troublesome

[dfeinzimer]

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If the content provided to the Floating Panel isn't placed within some from of container then there's unexpected behavior. The selected detent doesn't work properly and the resize handle moves out of sync with the finger location.

With container

// initial detent set to half
VStack {
    Text("Title")
    List {
        Text("Item 1")
        Text("Item 2")
        Text("Item 3")
    }
}

Without container

// initial detent set to half
Text("Title")
List {
    Text("Item 1")
    Text("Item 2")
    Text("Item 3")
}