WIP: feature to use offline installer

[miurahr]

Trial to integrate CuteCI installation logics into aqtinstall.
This is incomplete.

There will be no further work without any contribution from one who have a knowledge and experiments about offline_installer.

[miurahr]

For Linux execution, it fails with following 'Could not connect to display' error. Does anyone know how to run in headless?

2021-05-25 04:36:32,090 - aqt - INFO - aqtinstall(aqt) vunknown on Python 3.9.5 [CPython GCC 9.3.0]
2021-05-25 04:36:32,090 - aqt - WARNING - Cannot find /home/runner/.local/share/Qt/qtaccount.ini
2021-05-25 04:36:32,090 - aqt - INFO - Download Qt https://download.qt.io/new_archive/qt/5.6/5.6.3/qt-opensource-linux-x64-5.6.3.run
2021-05-25 04:37:34,349 - aqt - INFO - Running installer /home/runner/work/aqtinstall/aqtinstall/qt-opensource-linux-x64-5.6.3.run ['/home/runner/work/aqtinstall/aqtinstall/qt-opensource-linux-x64-5.6.3.run', '--script', '/home/runner/work/aqtinstall/aqtinstall/aqt/install-qt.qs', '--platform', 'minimal']
QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/tmp/runtime-runner'
QXcbConnection: Could not connect to display 
2021-05-25 04:37:34,615 - aqt - ERROR - Installer error: -6

[miurahr]

An installer on Windows does not finish the task in 80min.

[miurahr]

no further information given, so it is not valuable to continue to dev.