[MAYA-112349] Ability to hide Prims from UFE so they do not show in the outliner

We use a USD proxy workflow in our layout and set dressing system. Assets contain both a render purpose sub tree and a proxy purpose subtree. We do this to allow the efficient layout of very large sets with very heavy render geometry.

It can be confusing for artists when the viewport displays a proxy mesh but the outliner shows the prims of the renderable mesh. They try and manipulate the renderable mesh while viewing the proxy, which can cause the proxy mesh to be offset from the renderable mesh, especially when the proxy is not very low poly ( but still much lower then the renderable mesh). Switching the UsdProxyShape from Proxy to Render purpose display is undesirable as scenes can be so heavy they lock up when viewing all renderable meshes.

In our current system we hide the children of render meshes with a proxy while the proxy is displayed. This means the artist can’t make a mistake and select the render mesh. We support editing the render mesh by toggling its purpose to default and hiding the proxy subtree. This allows per asset proxy visibility.

To support this workflow we would like some way to hide or stop UFE traversal so when a asset is in proxy mode the sub prims of the asset are hidden.

We are using the kind selection option var to limit selection to the asset kind which is above the proxy and render prim but this only helps with viewport selection and not outliner selection where all prims are visible.

Start by tracing UFE traversal and outliner selection for the USD proxy and render-purpose prims, including the UsdProxyShape and kind-selection behavior mentioned in the issue. Done means providing a way for proxy-mode assets to hide or stop traversal of their render subprims in the outliner while preserving the described render-mesh editing workflow.

Written by the indexing model from the issue text.