Fix widgets being leaked by the ToolChainOptionsPage.
This page created widgets and stored them in the tree node
and never deleted them.
The fix is to put all the widgets into one QStackedWidget, so
that this will clean up once the page is destroyed.
Change-Id: Ic02824a4c52771d8962dc594176077c2e139fb84
Reviewed-by: Tobias Hunger <tobias.hunger@qt.io>
This allows for use of the new SettingsAccessor infrastructure for
upgrading, backups, etc.
Task-number: QTCREATORBUG-20148
Change-Id: I5419c86c0fd576a59ec91c212097c8f987e01da2
Reviewed-by: Eike Ziller <eike.ziller@qt.io>
