feat: option to use Alt+[0-9] to select service

[dxrcy]

Closes #1971, and shares similarity with #1920

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Description of Change

Add an option to Settings > Advances > Shortcuts to use Alt modifier (instead of Ctrl) to select current service with number keys.
The input is unchecked by default. If the input is checked, the user cannot use Ctrl+[0-9] to activate a service, but instead must use Alt+[0-9] (similar to Firefox). This does not impact users who do not manually enable the feature.

I have placed the toggle option below the shortcut inputs implemented by #1920 because it seems the most appropriate location. Likewise the state is stored in stores.shortcuts. This can of course be changed if deemed necessary.

Motivation and Context

I use Firefox, so I am accustomed to using Alt+[0-9] to switch tabs (rather than Ctrl+[0-9]).
Closes #1971 by implementing the second proposed solution (issue provides 3 possible solutions).

Screenshots

Checklist

• My pull request is properly named
• The changes respect the code style of the project (pnpm prepare-code)
• pnpm test passes
• I tested/previewed my changes locally

Release Notes

Add option to use Alt+[0-9] to select service.