refac: TreeIndexToSectorMap optimize

[Strepto]

Type of change

Jira ticket 📘

https://cognitedata.atlassian.net/browse/

Description 📝

Builds upon the changes in #3695 , consider reviewing that first

Allocating a new Set for each treeindex in the model has some memory overhead when profiled.

Stats for a custom sample model scene in the reveal "example" viewer:

See JS Heap Size

Initial load of custom 3d model for profiling.

More stats for the camera viewpoint I took all profilings from:
Unique treeIndexes: 347012 Average sectors per treeIndex 1.0567 (The scene.json has ~2.3 million treeindexes so this is just a subset)

Distribution of sectors per TreeIndex in the loaded sectors

1: 327558  (Read: 327558 (>90%) treeindexes are in just 1 sector)
2: 19232 
3: 197 
4: 24 
5: 1 

When we have so few items the set.has vs array.contains becomes equal or better for array. And the overhead of an Set vs array is considerable when we have millions of them.

How has this been tested? 🔍

Unit test coverage should cover the use.

Tested in browser, and found no performance regression (possible perf increase) and found significant memory saving.

Test instructions ℹ️

Checklist ☑️

• I am proud of this feature.
• I have performed a self-review of my own code.
• I have added PR type (Feat, Bug, Chore, Test, Docs, Style, Refactor) to the PR title.
• I have manually tested this for different scenarios (different models, formats, devices, browsers).
• I have commented my code in hard-to-understand areas.
• I have made corresponding changes to the public documentation.
• I have added unit and visuals tests to prove that my feature works to the best of my ability.
• I have refactored the code for readability to the best of my ability.
• I have checked that my changes do not introduce regressions in the public documentation.
• I have outlined any known defects / lacking capabilities in the contents of this PR.
• I have listed any remaining work that should follow this PR in the description or jira/miro/etc.
• I have added TSDoc to any public facing changes.
• I have added "developer documentation" in any package README.md that is related / applicable to this PR.
• I have noted down and am currently tracking any technical debt introduced in this PR.
• I have thoroughly thought about the architecture of this implementation.
• I have asked peers to test this feature.

[codecov]

Codecov Report

Merging #3697 (3d19a0d) into master (887b847) will increase coverage by 0.00%.
Report is 41 commits behind head on master.
The diff coverage is 87.50%.

@@           Coverage Diff           @@
##           master    #3697   +/-   ##
=======================================
  Coverage   71.70%   71.71%           
=======================================
  Files         346      346           
  Lines       33762    33766    +4     
  Branches     2650     2650           
=======================================
+ Hits        24210    24214    +4     
  Misses       9445     9445           
  Partials      107      107           

Files	Coverage Δ
...s/cad-model/src/utilities/TreeIndexToSectorsMap.ts	100.00% <100.00%> (ø)
viewer/packages/cad-model/src/wrappers/CadNode.ts	86.40% <100.00%> (ø)
...packages/cad-model/src/wrappers/CogniteCadModel.ts	78.65% <0.00%> (ø)

[haakonflatval-cognite]

LGTM 👍

I ran some tests - they showed a slightly higher average FPS, while the memory use is much smaller. Nice contribution!