[WIP] Container base record mutations

[Assumeru]

Continuation of #2870 https://gitlab.com/OpenMW/openmw/-/issues/2798

Some of these might get fixed along the way
https://gitlab.com/OpenMW/openmw/-/issues/2404
https://gitlab.com/OpenMW/openmw/-/issues/3862
https://gitlab.com/OpenMW/openmw/-/issues/3929

[Assumeru]

So it turns out scripted items in containers have been broken since they were initially implemented. The scripts don't start running till the container is opened.

Features be creeping.

Edit: Or not. Vanilla doesn't run them after saving and reloading.

[psi29a]

/home/travis/build/OpenMW/openmw/apps/openmw/mwscript/containerextensions.cpp: In member function ‘virtual void MWScript::Container::OpAddItem<R>::execute(Interpreter::Runtime&)’:
/home/travis/build/OpenMW/openmw/apps/openmw/mwscript/containerextensions.cpp:71:69: error: ‘const class MWWorld::Class’ has no member named ‘getContainerStore’
   71 |                     MWWorld::ContainerStore& store = ptr.getClass().getContainerStore (ptr);
      |                                                                     ^~~~~~~~~~~~~~~~~
/home/travis/build/OpenMW/openmw/apps/openmw/mwscript/containerextensions.cpp: In member function ‘virtual void MWScript::Container::OpGetItemCount<R>::execute(Interpreter::Runtime&)’:
/home/travis/build/OpenMW/openmw/apps/openmw/mwscript/containerextensions.cpp:134:69: error: ‘const class MWWorld::Class’ has no member named ‘getContainerStore’
  134 |                     MWWorld::ContainerStore& store = ptr.getClass().getContainerStore (ptr);
      |                                                                     ^~~~~~~~~~~~~~~~~
/home/travis/build/OpenMW/openmw/apps/openmw/mwscript/containerextensions.cpp: In member function ‘virtual void MWScript::Container::OpRemoveItem<R>::execute(Interpreter::Runtime&)’:
/home/travis/build/OpenMW/openmw/apps/openmw/mwscript/containerextensions.cpp:169:69: error: ‘const class MWWorld::Class’ has no member named ‘getContainerStore’
  169 |                     MWWorld::ContainerStore& store = ptr.getClass().getContainerStore(ptr);
      |                                                                     ^~~~~~~~~~~~~~~~~
/home/travis/build/OpenMW/openmw/apps/openmw/mwscript/containerextensions.cpp: In member function ‘virtual void MWScript::Container::OpEquip<R>::execute(Interpreter::Runtime&)’:
/home/travis/build/OpenMW/openmw/apps/openmw/mwscript/containerextensions.cpp:238:45: error: ‘const class MWWorld::Class’ has no member named ‘getContainerStore’
  238 |                         it = ptr.getClass().getContainerStore (ptr).add (item, 1, ptr);
      |                                             ^~~~~~~~~~~~~~~~~

[Assumeru]

Oh yeah, that's just my note-to-self-fix-this-stuff 😃

Note to self: fix memory leak below

[Assumeru]

Exiled to https://gitlab.com/OpenMW/openmw/-/merge_requests/353