AK: Add dbgln() format checking

This checks the following things:
- No unclosed braces in format string
    `dbgln("a:{}}", a)` where the '}}' would be interpreted as a
    literal '}'
    `dbgln("a:{", a)` where someone with a faulty keyboard like mine
    could generate
- No extra closed braces in format string
    `dbgln("a:{{}", a)` where the '{{' would interpreted as a literal '{'
    `dbgln("a:}", a)` where someone with a faulty keyboard could
    generate
- No references to nonexistent arguments
    `dbgln("a:{} b:{}", a)` where the value of `b` is not in the
    arguments list
- No unconsumed argument
    `dbgln("a:{1}", not_used, 1)` where `not_used` is extraneous

AK/String.h

@@ -275,7 +275,10 @@ public:
     }
 
     template<typename T>
-    static String number(T value) requires IsArithmetic<T>::value { return formatted("{}", value); }
+    static String number(T value) requires IsArithmetic<T>::value
+    {
+        return formatted("{}", value);
+    }
 
     StringView view() const;