[clang-format] Update GoogleStyle for C# code to match Google's internal C# style guide

Summary: Google's C# style guide is at https://google.github.io/styleguide/csharp-style.html

Reviewers: krasimir, MyDeveloperDay, sammccall

Reviewed By: MyDeveloperDay

Subscribers: cfe-commits, klimek

Tags: #clang-format, #clang

Differential Revision: https://reviews.llvm.org/D79715