[clang-format] Add option WrapNamespaceBodyWithNewlines (#106145)

It wraps the body of namespace with additional newlines, turning this code:
```
namespace N {
int function();
}
```
into the following:
```
namespace N {

int function();

}
```

---------

Co-authored-by: Owen Pan <owenpiano@gmail.com>

1 files changed, 7 insertions, 0 deletions

diff --git a/clang/unittests/Format/ConfigParseTest.cpp b/clang/unittests/Format/ConfigParseTest.cpp
index b249bf0..9c38dbb 100644
--- a/clang/unittests/Format/ConfigParseTest.cpp
+++ b/clang/unittests/Format/ConfigParseTest.cpp
@@ -865,6 +865,13 @@ TEST(ConfigParseTest, ParsesConfiguration) {
   CHECK_PARSE("SortUsingDeclarations: true", SortUsingDeclarations,
               FormatStyle::SUD_LexicographicNumeric);
 
+  CHECK_PARSE("WrapNamespaceBodyWithEmptyLines: Never",
+              WrapNamespaceBodyWithEmptyLines, FormatStyle::WNBWELS_Never);
+  CHECK_PARSE("WrapNamespaceBodyWithEmptyLines: Always",
+              WrapNamespaceBodyWithEmptyLines, FormatStyle::WNBWELS_Always);
+  CHECK_PARSE("WrapNamespaceBodyWithEmptyLines: Leave",
+              WrapNamespaceBodyWithEmptyLines, FormatStyle::WNBWELS_Leave);
+
   // FIXME: This is required because parsing a configuration simply overwrites
   // the first N elements of the list instead of resetting it.
   Style.ForEachMacros.clear();