Add pending restoration for default browser.

By keeping the restored default browser package name in the original
Settings field, and applying it post package install. A little bit of
renaming is done to make this more evident.

Setting the default browser is also changed to async since there's no
reason to block system server main thread for that.

Also simplified DefaultAppProvider.setDefaultBrowser() since we no
longer have any API that requires the operation to complete
synchronously.

Fixes: 271337188
Test: manual
Change-Id: I197e8b523f9f7f99bffe2e3c3608507e754ff60a