internal: new shared_ptr and weak_ptr implementation (#5883)

moves std::shared_ptrs to a new implementation

Advantages:
- you can dereference a weak_ptr directly. This will obviously segfault on a nullptr deref if it's expired.
   - this is useful to avoid the .lock() hell where we are 100% sure the pointer _should_ be valid. (and if it isn't, it should throw.)
- weak_ptrs are still valid while the SP is being destroyed.
   - reasoning: while an object (e.g. CWindow) is being destroyed, its `weak_ptr self` should be accessible (the sp is still alive, and so is CWindow), but it's not because by stl it's already expired (to prevent resurrection)
   - this impl solves it differently. w_p is expired, but can still be dereferenced and used. Creating `s_p`s is not possible anymore, though.
   - this is useful in destructors and callbacks.

src/desktop/Window.hpp

@@ -467,7 +467,7 @@ inline bool valid(PHLWINDOW w) {
 }
 
 inline bool valid(PHLWINDOWREF w) {
-    return w.lock().get();
+    return !w.expired();
 }
 
 inline bool validMapped(PHLWINDOW w) {
@@ -479,7 +479,7 @@ inline bool validMapped(PHLWINDOW w) {
 inline bool validMapped(PHLWINDOWREF w) {
     if (!valid(w))
         return false;
-    return w.lock()->m_bIsMapped;
+    return w->m_bIsMapped;
 }
 
 /**