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

[Owen Pan via cfe-commits]

================
@@ -28430,6 +28430,36 @@ TEST_F(FormatTest, ShortNamespacesOption) {
       "}}} // namespace foo::bar::baz",
       "namespace foo { namespace bar { namespace baz { class qux; } } }",
       Style);
+  Style.FixNamespaceComments = false;
+
+  Style.BreakBeforeBraces = FormatStyle::BS_Custom;
+  Style.BraceWrapping.AfterNamespace = true;
+  verifyFormat("namespace foo { class bar; }", Style);
+  verifyFormat("namespace foo { namespace bar { class baz; } }", Style);
+  verifyFormat("namespace foo\n"
+               "{ // comment\n"
----------------
owenca wrote:

Changing this line to:
```c++
//
{
```
would result in:
```
With diff:
@@ -1,5 +1,3 @@
 namespace foo
 //
-{
-class bar;
-}
+{ class bar; }
```

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