python/357 has bullets submodels which are animated using parent bones.
Their direct bones are static, and thus the entire submodel was picked
up as static.
Now when computing bone transform for particular sequence/anim frame
also merge it with parent transform. Bones are laid out sequentially in
their "dependency order" so using a direct parent is fine, as it also
contains its parent transforms.
Fixes: #554
Sometimes the initial list of models doesn't contain everything that is
used later. I don't know why. So detect this and allow loading model
infos later.
Fixes#546
Add render refcount to submodels to diagnose when it can't properly clear things due to them being used somewhere still.
Also add `speeds.submodels_cache_{dynamic,static}` counters to show how many submodels render models have been allocated.
Gives out individual render submodels for dynamic ones, receives and remembers them when they are not needed anymore.
Stores only one render submodel for static ones. Reuses/instantiates it for everyone.
Detect whether studio model has changed, and replace it with a new one.
It does (as predicted) run into a gpu sync issue if reuse happened while previous frame with the old user is still being drawn.
Ivan Avdeev