Resolve "QLayout: Attempting to add QLayout "" to otb::Wrapper::QtWidgetParameterGroup "", which already has a layout"

Summary

Create QLayout without a parent in the constructor, as is done in QT documentation.

Rationale

Closes #1645 (closed)

Implementation Details

The QLayout constructor sets the parent's widget layout to this. In MR !125 (merged) I added this as default parent to all QObjects (including QLayouts) to avoid potential memory leaks. This is bad idea for layouts because a widget's layout cannot be changed without removing the existing one first. This causes the warning reported in #1645 (closed) for QtWidgetView and QtWidgetParameterGroup because they create a layout not intended for this. When adding a layout to this later, the warning is emitted.

Additional notes

Copyright

The copyright owner is CNES and has signed the ORFEO ToolBox Contributor License Agreement.

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Check before merging:

• All discussions are resolved
• At least 2 votes from core developers, no vote.
• The feature branch is (reasonably) up-to-date with the base branch
• Dashboard is green
• Copyright owner has signed the ORFEO ToolBox Contributor License Agreement

added bug label

changed the description

dashboard green, needs votes

changed the description

merged

mentioned in commit 8f948ac6

mentioned in issue #1722 (closed)

changed milestone to %7.0.0