Slow opening of quick type hierarchy view for lots of classes

In our project (about ~2000 plugins and features) we have very large and deep inheritance hierarchies. When opening the quick type hierarchy view (`ctrl+t`) on some methods, it takes a very long time to open the view and Eclipse ui freezes while the view is being opened.

See this sample of opening a method in our project, about 120s to render the view on `4.38.0.v20251020-1800` on a windows machine:

This issue boils down to the fact that the view expands an extremely large inheritance tree (about 17000 classes) when opening.
The fix from #1954 for related issue #1830 does not apply to this situation because there are no duplicate subtrees involved.

Reproduce the delay by opening the quick type hierarchy with Ctrl+T on a method in a project with a large inheritance tree. Compare the behavior with the related context from #1954 and #1830, then verify that the hierarchy opens without a prolonged Eclipse UI freeze when expanding roughly 17,000 classes.

Written by the indexing model from the issue text.