Also:
- Remove unused `button_click` event handler in `AcceptEuaDialog`
- Load EUAs within the `UpgradeRequiresEua` `Check` and removed the spinner from `AcceptEuaDialog`
- Remove `_errors` from `AcceptEuaDialog`
Signed-off-by: Danilo Del Busso <danilo.delbusso@cloud.com>