Add redundantViewBuilder rule

[miguel-jimenez-0529]

Summary

Add redundantViewBuilder rule to remove redundant @ViewBuilder attributes in SwiftUI code.

@ViewBuilder is implicit on View.body properties and ViewModifier.body(content:) functions, and is unnecessary on single-expression properties or functions.

// WRONG
struct PlanetView: View {
  @ViewBuilder
  var body: some View {
    Text("Hello, World!")
  }

  @ViewBuilder
  var subtitle: some View {
    Text("Subtitle")
  }
}

// RIGHT
struct PlanetView: View {
  var body: some View {
    Text("Hello, World!")
  }

  var subtitle: some View {
    Text("Subtitle")
  }
}

// ALSO RIGHT: @ViewBuilder is necessary for conditionals
struct ConditionalView: View {
  var showDetails: Bool

  var body: some View {
    title
  }

  @ViewBuilder
  var title: some View {
    if showDetails {
      Text("Details")
    } else {
      Text("Summary")
    }
  }
}

Reasoning

• @ViewBuilder is automatically applied by the compiler to View.body and ViewModifier.body(content:), so adding it explicitly is redundant
• Single-expression properties and functions don't need @ViewBuilder since there's only one view being returned
• Removing unnecessary attributes reduces visual noise and keeps code clean

SwiftFormat rule: nicklockwood/SwiftFormat#2297

[calda]

Perfect, thank you!