Compound - Swift 6.2 and Main actor isolation (#5109)

* compound is now using 6.2 and main actor isolation + some tweaks to make it build tests and EX

* better handling of the nonisolated context for CompoundUIColors

* improving docs

* fix comment

* remove unused Sendable conformance

ElementX/Sources/Screens/Timeline/View/Style/TimelineItemBubbleBackground.swift

@@ -16,10 +16,10 @@ extension View {
     ///   - color: self explanatory, defaults to subtle secondary
     func bubbleBackground(isOutgoing: Bool = true,
                           insets: EdgeInsets = .init(top: 8, leading: 12, bottom: 8, trailing: 12),
-                          color: Color? = .compound.bgSubtleSecondary) -> some View {
+                          color: @autoclosure @MainActor () -> Color? = .compound.bgSubtleSecondary) -> some View {
         modifier(TimelineItemBubbleBackgroundModifier(isOutgoing: isOutgoing,
                                                       insets: insets,
-                                                      color: color))
+                                                      color: color()))
     }
 }