Remember files that timed out in Tern

This is a squashed version of PR https://github.com/adobe/brackets/pull/8198. See for more comments.

This is to finish Trello Card: https://trello.com/c/2ra9FzGL/1284-m-js-code-hints-automatic-crash-preventer
Following up on the previous discussion, I think we *would* want these exclusions to show up in UI. That way, if the user has reason to believe that the automatically excluded files may now work correctly, they'd be able to remove them easily via the UI.