* remove `string.IsNullOrEmpty(OS.ShellOrTerminal)` checking from detail backend since it has been checked by `Native.OS.OpenTerminal`
* remove `ViewModels.Preference.IsTerminalConfigured` because it is only used by itself (Unlike `IsGitConfigured`).
* add `Native.OS.TestShellOrTerminal` and use it instead of setting `Preference.ShellOrTerminal` directly, because we have binded a callback that will save preference into file when its property changed. It may cause lag in some enviroments if we saving preference into file too frequently (see PR #436).
* run `dotnet format`
