GUI: Add a way to delete saved games from the save/load game grid view

[Thunderforge]

When saving or loading a game from the grid view, there is no option to delete a saved game. The only way to do that is to switch to a list view, select the game, and then click the "Delete" button.

I would like to request adding a way to delete a game from the grid view.

Reproduction steps

1. Create a save in a game that has ​enhanced save/load support.
2. Go back to the launcher main menu
3. Click the "Load" button
4. If on the List view, click the Grid view button in the bottom left

Note that there is no option to delete a game.

(Tested on ScummVM 2.5.1 and 2.6.0 Nightly 2022-05-25)

Possible Solutions

1. Add a right-click context menu with a "Delete" option when right-clicking on a saved game
2. Add a trash can icon near the save file, perhaps only visible when hovering over it
3. Change the behavior so that instead of a single click on the save game resulting in a load, instead it behaves like the list view:
   • A double-click loads the game
   • A single click highlights the game, but does not load it. From there, a newly added "Delete" button can delete the game