The destroy callback handler of Dock bar item for plugin doesn't make sense

[zxkmm]

Describe the problem

The destroy callback handler of Dock bar item for plugin doesn't make sense
Cuz there's no scene that apply "destroy" a Dock bar, cuz it cannot be destried whatsoever, hence there's no "delete" dock thing exist

solutions

• either add a hide and show callback and keep the destroy one as is.
• or make the destroy response Dock item hide ev and init when un-hide again.

刚才想了一下似乎第一种solution更合理，因为书签+插件似乎不会希望每次隐藏都销毁