Add global using for "System"
Note: It is now not necessary to write `using System;` in *.cs files. So when it is unused, it's not necessary to remove it. And when it is needed, you don't need to add it.
ADD
WalletWasabi.Backend/GlobalUsings.cs
+global using System;

ADD
WalletWasabi.Fluent.Desktop/GlobalUsings.cs
+global using System;

ADD
WalletWasabi.Fluent.Generators/GlobalUsings.cs
+global using System;

ADD
WalletWasabi.Fluent/GlobalUsings.cs
+global using System;

ADD
WalletWasabi.Gui/GlobalUsings.cs
+global using System;

ADD
WalletWasabi.Packager/GlobalUsings.cs
+global using System;

ADD
WalletWasabi.Tests/GlobalUsings.cs
+global using System;

ADD
WalletWasabi/GlobalUsings.cs
+global using System;

Add global using for "System"

Note: It is now not necessary to write `using System;` in *.cs files. So when it is unused, it's not necessary to remove it. And when it is needed, you don't need to add it.