Need to clean up temporary XPI files.

[ndanner-wesleyancs]

It looks like geckodriver does not clean up the temporary copy of the extension XPI file that it creates when it is installed. That results in a copy of the file being left in /tmp for every browser that is run. This needs a workaround.

See https://gitlab.com/ajacewicz/similarity_phish_detect/-/issues/10 for preliminary discussion (the problem was discovered while developing that crawl infrastructure), and openwpm#1090 for the issue on the main OpenWPM repo. I'm using this issue for recording my work on it.

[ndanner-wesleyancs]

Looks like shutdown_browser is not called if there is a problem during the site visit, so that isn't a good place to delete the temporary directory. But close_browser_manager is called, so maybe that is a better place. But then why is the profile directory deleted in shutdown_browser? And how is it getting deleted under the same circumstances?