refactor(android): remove "WebViewClient.jar" from SDK

[jquick-axway]

JIRA:
https://jira.appcelerator.org/browse/TIMOB-28241

Summary:

• This JAR was used to handle WebView client certificate requests on Android 4.x.
• Now that Titanium's min OS version has been raised to Android 5.0, JAR is no longer needed.
• Replaced AsyncTask with Thread since we were only using task's doInBackground() method.

Test:

1. Build and run the below on Android.
2. Tap on the "Download Certificate" button.
3. Tap on the badssl.com-client.p12 link.
4. If Android asks for a password then enter: badssl.com
5. Go to Android's system Settings -> Security -> Advanced -> Encryption & Credentials screen.
6. Tap on Install Certificate -> VPN & app user certificate screen.
7. Select downloaded certificate from "Downloads" folder and install it.
8. Note that you might need to enable a passcode/PIN on the device.
9. Go back to the Titanium app.
10. Tap on the "Show WebView" button.
11. Verify an alert dialog is shown asking for a certificate.
12. Select the installed certificate.
13. Verify that a green webpage is shown. (A red webpage is shown if client certificate is NOT selected.)

const parentWindow = Ti.UI.createWindow();
const downloadButton = Ti.UI.createButton({
	title: "Download Certificate",
	top: "30%",
});
downloadButton.addEventListener("click", () => {
	Ti.Platform.openURL("https://badssl.com/download/");
});
parentWindow.add(downloadButton);
const webButton = Ti.UI.createButton({
	title: "Show WebView",
	bottom: "30%",
});
webButton.addEventListener("click", () => {
	const webWindow = Ti.UI.createWindow();
	webWindow.add(Ti.UI.createWebView({
		url: "https://client.badssl.com/",
		width: Ti.UI.FILL,
		height: Ti.UI.FILL,
	}));
	webWindow.open();
});
parentWindow.add(webButton);
parentWindow.open();

[build]

	Messages
📖	✊ The commits in this PR match our conventions! Feel free to Rebase and Merge this PR when ready.
📖	✅ All tests are passing Nice one! All 14414 tests are passing. (There are 961 skipped tests not included in that total)
📖	💾 Here's the generated SDK zipfile.
📖	👍 Hey!, You deleted more code than you added. That's awesome!

Generated by 🚫 dangerJS against 909e807

[garymathews]

CR: PASS

[lokeshchdhry]

FR Passed.