Display objects from extensions in the new object dialog

[D8H]

Stories

• https://gdevelop-storybook.s3.amazonaws.com/object-list-with-extension/latest/index.html?path=/story/objecteditor-newbehaviordialog--with-community-extensions
• https://gdevelop-storybook.s3.amazonaws.com/object-list-with-extension/latest/index.html?path=/story/objecteditor-newbehaviordialog--default-for-sprite-object
• https://gdevelop-storybook.s3.amazonaws.com/object-list-with-extension/latest/index.html?path=/story/assetstore-extensionstore--with-community-extensions

Changes

• Extension, behavior and object lists now follow the same layout
• Assets are suggested for most custom objects
• Fix private objects not appearing in the list from within the extension