[clang] [clang-format] Support BraceWrapping.AfterNamespace with AllowShortNamespacesOnASingleLine (PR #123010)

[Owen Pan via cfe-commits]

owenca wrote:

Please fix the warning:
```
clang/lib/Format/UnwrappedLineFormatter.cpp:681:31: warning: comparison of integers of different signs: 'typename iterator_traits<AnnotatedLine *const *>::difference_type' (aka 'long') and 'const size_t' (aka 'const unsigned long') [-Wsign-compare]
  681 |       if (std::distance(I, E) <= N)
      |           ~~~~~~~~~~~~~~~~~~~ ^  ~
```

https://github.com/llvm/llvm-project/pull/123010