Fix cookie logic for webviews

Clear cookies before webview is started and load the webview in the
async response after cookie clearing is complete.
Remove unnecessary webview and cookie cleanup code.
Set the default webview client to prevent system browser redirects

Test: manual verify hyperlink does not open in system browser
Test: manual verify through IODT testing
Bug: 282129516
Change-Id: Ifee0d702440e89aa07196fefa810d85a64899493