Add rule to prefer a generated EnvironmentValue property implementation when possible

[miguel-jimenez-0529]

Summary

This PR adds a new rule to prefer using a generated EnvironmentValues property implementation.

This rule is implemented by the new environmentEntry SwiftFormat rule added in nicklockwood/SwiftFormat#1908.

/// WRONG: The `EnvironmentValues` property depends on `IsSelectedEnvironmentKey`
struct IsSelectedEnvironmentKey: EnvironmentKey {
  static var defaultValue: Bool { false }
}

extension EnvironmentValues {
  var isSelected: Bool {
   get { self[IsSelectedEnvironmentKey.self] }
   set { self[IsSelectedEnvironmentKey.self] = newValue }
  }
}

/// RIGHT: The `EnvironmentValues` property uses the @Entry macro 
extension EnvironmentValues {
 @Entry var isSelected: Bool = false
}

Reasoning

Manually-implemented environment keys are verbose and it is considered a legacy pattern. @Entry was specifically intended to be a replacement considering it was back ported to iOS 13.

[calda]

Remember to update airbnb.swiftformat and the SwiftFormat build before we merge this!

[calda]

Love it! Nice work!