[clang-format] Do not merge short C# class definitions into one line

Summary: Skip access specifiers before record definitions when deciding whether
or not to wrap lines so that C# class definitions do not get wrapped into a
single line.

Reviewers: krasimir, MyDeveloperDay

Reviewed By: krasimir

Tags: #clang-format

Differential Revision: https://reviews.llvm.org/D74050