Draft: Add macOS support

This MR contains Bindings.xcframework build manually from client repo, using the following script:

go mod tidy
rm -rf vendor/
go build ./...
go get golang.org/x/mobile/bind
go install golang.org/x/mobile/cmd/gomobile@latest
gomobile init
gomobile bind -target ios,iossimulator,macos gitlab.com/elixxir/client/bindings

go version go1.17.13 darwin/arm64

Sources/XXMessengerClient/Messenger/Functors/MessengerDestroy.swift

+import XCTestDynamicOverlay
+
+public struct MessengerDestroy {
+  public var run: () throws -> Void
+
+  public func callAsFunction() throws -> Void {
+    try run()
+  }
+}
+
+extension MessengerDestroy {
+  public static func live(_ env: MessengerEnvironment) -> MessengerDestroy {
+    MessengerDestroy {
+      env.ud.set(nil)
+      env.e2e.set(nil)
+      env.cMix.set(nil)
+      try env.fileManager.removeDirectory(env.storageDir)
+    }
+  }
+}
+
+extension MessengerDestroy {
+  public static let unimplemented = MessengerDestroy(
+    run: XCTUnimplemented("\(Self.self)")
+  )
+}