update qapps/vapps to vue3 and quasar2

[newmann]

This method minimizes the changes to the original program structure

[acetousk]

@newmann Thanks for the PR.

One change since the original conception of vue3quasar2 is we created a new render mode called qvt2 and vuet2 and left qvt / vuet as it currently is to not break the existing functionality.

If this PR can be refactored to adjust for that change then I'd be happy to check it out again and in less time.

Let me know if you need anything for that.

[newmann]

If it is decided to add a new rendering mode, corresponding modifications are indeed necessary. The PR I submitted is not much different from the original approach, so it is recommended to use the original solution.

Since qvt2 is merely an upgrade of qvt, why should qvt be retained? Wouldn't it be better to upgrade them together? Or are there other plans?