This patch adds a publicly callable qt6_add_plugin() API to create
plugins. This API is meant to cover cases such as the plugandpaint
example.
This patch also renames qt_add_plugin to qt_internal_add_plugin in order
to avoid clashes with the public API. To avoid breaking the existing
projects, a compatibility wrapper function is enabled by default unless
QT_DISABLE_QT_ADD_PLUGIN_COMPATIBILITY is specified.
Fixes: QTBUG-82961
Change-Id: If5b564a8406c90434f1bdad0b8df76d3e6626b5f
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>
6fbeef4c6b