Add-on store: add warning dialog (#15246)
Summary of the issue:
Users should be informed of the risk of installing add-ons
Description of user facing changes
When opening the add-on store, a warning dialog is shown.
There is a checkbox to not show the warning again.
Description of development approach
Uses similar approach to the user stats dialog
Move banner creation to helper function
Added typing to guiHelper.BoxSizerHelper. Fix bug where if a StaticBoxSizer is used with an intflag of buttons, BoxSizerHelper.addDialogDismissButtons wouldn't work correctly
Add support for creating labelled checkboxes using the BoxSizerHelper, LabelledControlHelper and associateElements
Testing strategy:
Test banner using --disable-addons
Test with sample code in source code for addDialogDismissButtons bug.
Test the warning nag - ensure the checkbox to hide the warning works
