Investigations related to Qt6

[magnesj]

• [x] make sure all external libraries can be compiled and used with both Qt5 and Qt6
• [x] update appfwk to qt6
• [x] update ceeviz to qt6
• [ ] update cmake in ResInsight for qt6 - https://github.com/magnesj/ResInsight/pull/58
• [x] improve cmake configuration for qt6 https://doc.qt.io/qt-6/cmake-get-started.html Use qt_standard_project_setup() and qt_add_executable if possible
• [x] remove caf::OpenGLWidget as suggested in https://github.com/OPM/ResInsight/pull/11250

qwt

• [x] update qwt to qt6. Update submodule, and delete obsolete branches. Not sure if we should use the branch defined below
• [ ] use the following branch https://github.com/CeetronSolutions/qwt/tree/qwt-multiaxes-cmake

Under consideration

• replace nightcharts with qtcharts #10995

Installation and runtime bundling

https://www.qt.io/blog/deploying-to-linux-with-cmake

Resources

Native support in Qt for gprc, could probably simplify build configuration and usage in ResInsight https://doc-snapshots.qt.io/qt6-6.5/qtgrpc-index.html

OpenGL https://doc.qt.io/qt-6/opengl-changes-qt6.html

[magnesj]

Tested several binary distributions of Qt6 for Linux, but the glic dependencies did not match latest installed on CentOS7. Build of Qt 6.5.3 from source is investigated.