CMake Qt6 wizard templates should specify 3.16 as the minimum cmake version required

Some of the Qt 6 wizard templates currently don't have

cmake_minimum_required(VERSION 3.16)

which is required for Qt to work properly, as documented per https://codereview.qt-project.org/c/qt/qtdoc/+/569159

Specifically I see

qtquickapplication_compat/CMakeLists.txt
1:cmake_minimum_required(VERSION 3.14)

qtwidgetsapplication/CMakeLists.txt
1:cmake_minimum_required(VERSION 3.5)

consoleapp/CMakeLists.txt
1:cmake_minimum_required(VERSION 3.14)

These should say 3.16 when a Qt 6 kit is chosen.

Perhaps it should say 3.16 also for the non-Qt projects like plaincpp, but that's harder to justify.

I'm not sure what is the right Qt Creator component to assign this issue, so please re-assign if appropriate.