Add "Update" button to extension catalog cards if an older version is installed

[jandubois]

Right now the card will have a "Remove" button, but no way to upgrade to the new version. The user needs to remove the old version, and then install the extension again.

The "Upgrade" button should have the primary button styling, and the "Remove" button should be secondary (but still in red).

Not sure if we can/want to do anything about displaying the versions of the old/new extension, but that would not be part of this story.