closes#5903, refs #5409
- switch alert/notification component tests from unit to integration where appropriate
- rename `notifications.closeAll` to `notifications.clearAll` to better represent it's behaviour
- add concept of a "key" to alerts/notifications and ability to close only specified keys through notifications service
- close duplicate alerts/notifications before showing a new one
- specify a key for all existing alerts
- close failure alerts on successful retries
- clear all currently displayed alerts on successful sign-in
no issue
- standardize on "{TestType}: {ModuleType}: {module-name}" for test description strings
- standardize on `{module-name}-test.js` for test file names
- fix deprecation notices for ember component unit tests without explicit `unit: test` or `needs: []`
issue #5409
- change persistent/passive notification status to alert/notification
- replace showSuccess/Info/Warn/Error with showNotification/showAlert
- fix and clean up notification/alert components
