[Feature Request] Enhancements for Saving and State Management

Help me out with these features. I believe they’re currently not available:

1. Since SRAM isn’t written onto disk until you close the content or RetroArch itself (for disk safety reasons), it would be useful to have at least an option — perhaps under the Save State menu — to manually write SRAM to file. This would prevent progress loss during long play sessions and support players who prefer not to rely on save states.

2. Allow assigning hotkeys up to 4-button combos for actions such as Save State. Currently, only 1 button is allowed AFAIK.

3. In the Save State submenu, it would be helpful if "State Slot" could indicate which slots contain data — for example, by adding an asterisk (*) next to the slot number. Also, allow users to delete individual slots data. Currently, the only way to tell if a slot has data is to enable the "Save State Thumbnails" option, but if you prefer not to use thumbnails, there’s no way to see which slots are occupied.

Start by tracing the Save State submenu, SRAM persistence behavior, and hotkey handling described in the issue. Break the request into separate scopes for manual SRAM writes, multi-button hotkeys, and state-slot indicators/deletion; done means each requested behavior is implemented and its interactions with existing save-state options are verified.