[General] Avoid unnecessary config writes

[CommandMC]

This PR checks settings values passed to setSetting and skips re-writing the config file if they haven't changed.

In the process of this, I've applied a similar treatment our useSetting hook got to getSetting and setSetting, which in turn involved setting a proper default value for currentConfig. Since that can be either AppSettings or GameSettings, depending on whether we're editing the global or game-specific settings, I've also made AppSettings extend GameSettings (so even if we only have a GameSettings object under the hood, we can still interact with it like it's a Partial<AppSettings> (since that's what it is))

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Use the following Checklist if you have changed something on the Backend or Frontend:

• Tested the feature and it's working on a current and clean install.
• Tested the main App features and they are still working on a current and clean install. (Login, Install, Play, Uninstall, Move games, etc.)
• Created / Updated Tests (If necessary)
• Created / Updated documentation (If necessary)

[flavioislima]

Looks good.
Tested here and it is working fine.