[clang] clang-format: Add "AllowShortNamespacesOnASingleLine" option (PR #105597)

[Owen Pan via cfe-commits]

================
@@ -27981,6 +27981,118 @@ TEST_F(FormatTest, BreakBinaryOperations) {
                Style);
 }
 
+TEST_F(FormatTest, ShortNamespacesOption) {
+  FormatStyle Style = getLLVMStyle();
----------------
owenca wrote:

```suggestion
  auto Style = getLLVMStyle();
```

https://github.com/llvm/llvm-project/pull/105597