[Tree widget]: Fix subjects/models having partial visibility when always drawn exclusive is true

[JonasDov]

part of #1510.
This was happening when all conditions below were met:

1. Models' elements have categories and those categories don't have a single root element.
2. There are elements in always/never drawn list.
3. Some categories (from 1st step) are visible due to category selector or per model override.
4. Always drawn exclusive flag is set to true.

In such cases adding element to exclusive always drawn list would cause models of other elements to have partial visibility even though all elements of that model are not visible.

[github-actions]

Tree-Widget benchmark

Benchmark suite	Current: dee6234	Previous: 9f6e677	Deviation	Status
categories tree creates initial filtered view for 50k items	1499.26 ms	1333.65 ms	12.42%	🚨
categories tree creates initial filtered view for 50k items (P95 of main thread blocks)	454 ms	281 ms	61.57%	🚨
categories tree changing definition container visibility changes visibility for 50k subCategories	5964.54 ms	7562.56 ms	-21.13%	✅
categories tree changing definition container visibility changes visibility for 50k subCategories (P95 of main thread blocks)	51 ms	57 ms	-10.53%	〰️
categories tree changing definition container visibility changes visibility for 50k categories	7343.37 ms	10759.7 ms	-31.75%	✅
categories tree changing definition container visibility changes visibility for 50k categories (P95 of main thread blocks)	78 ms	97 ms	-19.59%	〰️
models tree creates initial filtered view for 50k target items	923.46 ms	817.99 ms	12.89%	🚨
models tree creates initial filtered view for 50k target items (P95 of main thread blocks)	115 ms	144 ms	-20.14%	〰️
models tree validates categories visibility for imodel with 50k categories	7806.63 ms	7821.27 ms	-0.19%	〰️
models tree validates categories visibility for imodel with 50k categories (P95 of main thread blocks)	82 ms	82 ms	0%	🟰
models tree changing model visibility changes visibility for 50k elements	2413.1 ms	2369.85 ms	1.83%	〰️
models tree changing model visibility changes visibility for 50k elements (P95 of main thread blocks)	0 ms	0 ms	0%	🟰
models tree changing category visibility changes visibility for 50k elements	2394.83 ms	2624.12 ms	-8.74%	〰️
models tree changing category visibility changes visibility for 50k elements (P95 of main thread blocks)	0 ms	121 ms	-100%	✅
models tree changing per-model-category override changes visibility for 50k elements	2354.25 ms	2489.13 ms	-5.42%	〰️
models tree changing per-model-category override changes visibility for 50k elements (P95 of main thread blocks)	0 ms	0 ms	0%	🟰
models tree changing element visibility changes only parent nodes visibility with 50k elements	4703.68 ms	4443.8 ms	5.85%	〰️
models tree changing element visibility changes only parent nodes visibility with 50k elements (P95 of main thread blocks)	97 ms	67 ms	44.78%	〰️

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