[DevTask] Add a `Generate More` button on result selection panel

[huchenlei]

Often it is tedious to create the selection again and re-run the process. It would be convenient to add a button on result selection panel along side with existing discard and pick to repeat the generation process for more results.

[huchenlei]

Implemented in https://github.com/huchenlei/stable-diffusion-ps-pea/commit/77cf8f080dde6f30ac7924dd836b18630d326295.

[huchenlei]