Issues and improvements for v1.6.x / Contao 5

[x] Install Tool should not be available in navigation if not supported (on Contao 5)
[x] Issues setting the user password on Windows (passwords do not match, maybe needs PHP_EOL instead of \n)
[x] ~Windows fails to update (Cannot rename "F:/public_html/c50/public/cm-test.temp" to "F:/public_html/c50/public/cm-test.phar.php".)~
[x] After installation, migrations and adding backend user, accessing the back end still redirects to the install tool to confirm the license and create an install-tool password.
[x] After running a task and updating schema, closing the schema screen redirects to maintenance (instead of the source/probably the packages list)
[x] ~We need to make sure an APP_SECRET is set when not using the install tool~ (https://github.com/contao/contao/pull/5066)
[x] Check database status when migrations are completed
[x] Handle database warnings and problems
[x] Do not show the "include drop queries" checkbox in migrations if there are no drop queries
[x] If exceptions (e.g. from third party bundles) happen in contao:migrate, we always show authentication error. Maybe we should (try to) detect the actual problem/at least access errors.
[x] Toggling the console of all migrations does not work (https://www.loom.com/share/27e650519dbb496a86fff494c045de5b)
[x] When running on windows, the web directory (Setup screen) shows e.g. C:\foo\bar/public but should show C:\foo\bar\public

contao / contao-manager