LibJS: Inline fast case for Value::to_{boolean,number,numeric,primitive}

These functions all have a very common case that can be dealt with a
very simple inline check, often avoiding the need to call an out-of-line
function. This patch moves the common case to inline functions in a new
ValueInlines.h header (necessary due to header dependency issues..)

8% speed-up on the entire Kraken benchmark :^)

Tests/LibJS/test-value-js.cpp

@@ -5,6 +5,7 @@
  */
 
 #include <LibJS/Runtime/Value.h>
+#include <LibJS/Runtime/ValueInlines.h>
 #include <LibTest/TestCase.h>
 
 using namespace JS;