`ComponentHandle` offers a richer API of common functions, such as
`show()`/`hide()` as well as the new `clone_strong()` - that should help
to prevent mistakely created strong reference that may cause leaks.
Fixes#188
This allows creating multiple windows for example, and it will allow for
showing windows in those tests that require a mapped window.
As a bonus, the run() function on generated components is not consuming
anymore.