Separate HandleMenuActivateEvent function call from HandleMenuCommandEvent function call
since first one might update some of menus. Also add call to HandleMenuDeActivateEvent function.

Delete action with Qt5MenuItem to reflect the change in actual menu.

Also update underlying qt-based menu from Qt5Menu::InsertItem function.

And update Qt5Menu::SetItemImage to work with different types of descendants of SalBitmap.
This code is shared between Qt5 and KDE5 plugins, but KDE5 plugin uses SvpSalBitmap instead of Qt5Bitmap.
New image conversion process is borrowed from GTK plugin code.
This approach is used in order to properly process transparency channel if it's present, and it is present usually.

This change also fixes tdf#120789.

Change-Id: Ifdc64c3e5d80782955b52e2da8fcff4844d2dc25
Reviewed-on: https://gerrit.libreoffice.org/63862
Tested-by: Jenkins
Reviewed-by: Katarina Behrens <Katarina.Behrens@cib.de>