[TIMOB-28241] Android: Remove "WebViewClient.jar" from SDK

*Summary:* We added a "WebViewClient.jar" to the SDK (link below) so that our Ti.UI.WebView could prompt the end-user for a certificate if requested by the server on Android OS 4.4 and older versions. https://github.com/appcelerator/titanium_mobile/tree/master/android/modules/ui/lib In Titanium 10.0.0, we plan on bumping up our min Android OS version supported from 4.4 to 5.0. This means we can remove the "WebViewClient.jar" and it's usage of its undocumented classes/methods. *To-Do:* Remove the "WebViewClient.jar" here... https://github.com/appcelerator/titanium_mobile/tree/master/android/modules/ui/lib Change our [TiWebViewClient](https://github.com/appcelerator/titanium_mobile/blob/master/android/modules/ui/src/java/ti/modules/titanium/ui/widget/webview/TiWebViewClient.java) class to derive from WebViewClient instead of the undocumented WebViewClientClassicExt class. Remove the undocumented onReceivedClientCertRequest() method [here](https://github.com/appcelerator/titanium_mobile/blob/4490c3ea8554ad50c60d410208d401723525d771/android/modules/ui/src/java/ti/modules/titanium/ui/widget/webview/TiWebViewClient.java#L329-L336) as well. Remove the dependency path to ./modules/ui/lib from our "build.gradle" file here. https://github.com/appcelerator/titanium_mobile/blob/master/android/titanium/build.gradle