Fix VPN toggle failures (#2979)

Task/Issue URL: https://app.asana.com/0/1207603085593419/1207629954356116/f

macOS PR: duckduckgo/macos-browser#2892
BSK PR: duckduckgo/BrowserServicesKit#858

## Description

The VPN toggle is sometimes failing silently, apparently due to a race condition created by calls to `sendProviderMessage` while the VPN is starting up.

This PR changes our logic to limit when those calls are made, since none of them make sense to call when the VPN is connecting.

DuckDuckGo.xcodeproj/project.pbxproj

@@ -9718,7 +9718,7 @@
 			repositoryURL = "https://github.com/DuckDuckGo/BrowserServicesKit";
 			requirement = {
 				kind = exactVersion;
-				version = 159.0.1;
+				version = 159.0.2;
 			};
 		};
 		9F8FE9472BAE50E50071E372 /* XCRemoteSwiftPackageReference "lottie-spm" */ = {