Rule Request: `explicit_view_spacing`

New rule request

Having migrated to SwiftUI, a major issue we encountered was not understanding (and subsequently remembering to account for) the fact that Spacer, and V/HStack variants had a non-zero default spacing. We've added a rule locally to enforce that spacing should be explicit to avoid unexpected behaviour.

Triggering examples:

Spacer()

VStack {
    Text("Hello World")
}

LazyHStack(
    alignment: .leading
) {
    Text("Hello World")
}

Non-triggering examples:

Spacer(minLength: 8)

Spacer(minLength: .zero)

VStack(spacing: 8) {
    Text("Hello World")
}

LazyHStack(
    alignment: .leading,
    spacing: .zero
) {
    Text("Hello World")
}

This should not be enabled by default as the default behaviour is desired in some applications.

Use the triggering and non-triggering SwiftUI snippets in the issue as acceptance cases, and locate SwiftLint’s existing rule registration and rule-test patterns first. The work is complete when the new rule detects implicit Spacer and stack spacing, accepts explicit spacing, and is not enabled by default.