Add braces to C++ single-line loops and conditionals (NFC) (#2973)

This makes code easier to read and more consistent between C++ and Java.
Also update clang-format settings to always add a line break (even if no braces are used).

wpiutil/src/test/native/cpp/sigslot/signal-tracking.cpp

@@ -45,7 +45,9 @@ namespace {
 
 int sum = 0;
 
-void f1(int i) { sum += i; }
+void f1(int i) {
+  sum += i;
+}
 struct o1 {
   void operator()(int i) { sum += 2 * i; }
 };