Remove DesignKit package (#1886)

- Move button styles to Compound
- Rename text style to AuthenticationTextStyle as its only in the auth flow.
- Add the brand colour locally for now until its included in Compound.

* Update snapshots.

---------

Co-authored-by: Stefan Ceriu <stefan.ceriu@gmail.com>

ElementX/Sources/Other/SwiftUI/Layout/FullscreenDialog.swift

@@ -149,7 +149,7 @@ struct FullscreenDialog_Previews: PreviewProvider, TestablePreview {
                 Text("Continue")
                     .font(.compound.bodyLGSemibold)
             }
-            .buttonStyle(.elementAction(.xLarge))
+            .buttonStyle(.compound(.primary))
             
             Button { } label: {
                 Text("More options")

ElementX/Sources/Other/SwiftUI/Views/PlaceholderAvatarImage.swift

@@ -14,10 +14,8 @@
 // limitations under the License.
 //
 
-import SwiftUI
-
 import Compound
-import DesignKit
+import SwiftUI
 
 struct PlaceholderAvatarImage: View {
     @Environment(\.redactionReasons) private var redactionReasons