Add an easier way to get both active & inactive views for a display

In OCIO v1, the Config getViews(display) method returned all views. This was considered a bug (per issue #67) and a fix was attempted in closed PR #324 and then finally fixed in PR #875 (as part of OCIO v2).

As a result, in OCIO 2.x, getViews only returns the active views. This is usually what an application would want.

However in some situations it is useful to get all the views (active & inactive). Currently there is this API to do that:
```
int getNumViews(ViewType type, const char * display) const;
const char * getView(ViewType type, const char * display, int index) const;
```
but it requires iterating over both the shared and per-display views for a display. It would be nice to have the equivalent of getNumDisplaysAll and getDisplayAll for views.