There are some inconcistencies in the application when it comes to
button UI elements because we're using `StatusButton` in some places,
in other we use `StyledButton`. The latter is the original
component we've created when we started out building Status
Desktop, but is planned to be removed entirely in favour of
`StatusButton`.
This commit replaces the usages of `StyledButton` with `StatusButton`
Move the onboarding/login state machine to the top level in main.qml, so that logout events can trigger new states.
Add Loader to statemachine so that each component is lazy-loaded. Initial tests saved 50MB of memory on startup.
Currently, logging out, then logging back in to the same or different account results in a doubling-up of chats/messages/wallet accounts. These need to be reset, however I need help doing that and it would delayed and blown out this PR further. This reset has been done for Onboarding and Login, but needs to be done for chats, wallet, mailservers, etc.