AK+Kernel: Rename try_make_weak_ptr to make_weak_ptr_if_nonnull

This matches the likes of the adopt_{own, ref}_if_nonnull family and
also frees up the name to allow us to eventually add OOM-fallible
versions of these functions.

Kernel/Library/ThreadSafeWeakPtr.h

@@ -229,7 +229,7 @@ struct Formatter<WeakPtr<T>> : Formatter<const T*> {
 };
 
 template<typename T>
-WeakPtr<T> try_make_weak_ptr(const T* ptr)
+WeakPtr<T> make_weak_ptr_if_nonnull(const T* ptr)
 {
     if (ptr) {
         return ptr->template make_weak_ptr<T>();