Remove ISettingsUtils and ISettingsPath interfaces (#44331)

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fix/what does it change/how was it tested (even manually, if necessary)?
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## Summary of the Pull Request

This PR removes the ISettingsUtils and ISettingsPath interfaces to
reduce some complexity. They only existed so the classes can be used
with moq. But this is also possible by using virtual methods which is
cleaner.

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## PR Checklist

- [ ] Closes: #xxx
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issues) -->
- [ ] **Communication:** I've discussed this with core contributors
already. If the work hasn't been agreed, this work might be rejected
- [x] **Tests:** Added/updated and all pass
- [ ] **Localization:** All end-user-facing strings can be localized
- [ ] **Dev docs:** Added/updated
- [ ] **New binaries:** Added on the required places
- [ ] [JSON for
signing](https://github.com/microsoft/PowerToys/blob/main/.pipelines/ESRPSigning_core.json)
for new binaries
- [ ] [WXS for
installer](https://github.com/microsoft/PowerToys/blob/main/installer/PowerToysSetup/Product.wxs)
for new binaries and localization folder
- [ ] [YML for CI
pipeline](https://github.com/microsoft/PowerToys/blob/main/.pipelines/ci/templates/build-powertoys-steps.yml)
for new test projects
- [ ] [YML for signed
pipeline](https://github.com/microsoft/PowerToys/blob/main/.pipelines/release.yml)
- [ ] **Documentation updated:** If checked, please file a pull request
on [our docs
repo](https://github.com/MicrosoftDocs/windows-uwp/tree/docs/hub/powertoys)
and link it here: #xxx

src/settings-ui/Settings.UI/ViewModels/NewPlusViewModel.cs

@@ -26,13 +26,13 @@ namespace Microsoft.PowerToys.Settings.UI.ViewModels
     {
         private GeneralSettings GeneralSettingsConfig { get; set; }
 
-        private readonly ISettingsUtils _settingsUtils;
+        private readonly SettingsUtils _settingsUtils;
 
         private NewPlusSettings Settings { get; set; }
 
         private const string ModuleName = NewPlusSettings.ModuleName;
 
-        public NewPlusViewModel(ISettingsUtils settingsUtils, ISettingsRepository<GeneralSettings> settingsRepository, Func<string, int> ipcMSGCallBackFunc)
+        public NewPlusViewModel(SettingsUtils settingsUtils, ISettingsRepository<GeneralSettings> settingsRepository, Func<string, int> ipcMSGCallBackFunc)
         {
             _settingsUtils = settingsUtils ?? throw new ArgumentNullException(nameof(settingsUtils));
 
@@ -228,7 +228,7 @@ namespace Microsoft.PowerToys.Settings.UI.ViewModels
 
         private Func<string, int> SendConfigMSG { get; }
 
-        public static NewPlusSettings LoadSettings(ISettingsUtils settingsUtils)
+        public static NewPlusSettings LoadSettings(SettingsUtils settingsUtils)
         {
             NewPlusSettings settings = null;