Optimize avatar complexity calculations

[akleshchev]

Avatar complexity can take a lot of time to calculate, optimize it

An example:

Avatar has a single mVisualComplexityStale flag, when it's set viewer recalculates all of the complexity, every texture, mesh, object, not just an added one or changed one. Even lod schanges can trigger this. Ideally state should be stored per object, at minimum simple additions shouldn't force full recalculation. Another options is to split compexity into sections (per joint, hud, textures)

Test plan

• Enable Advanced menu > Performance Tools > Show avatar complexity
• Make sure complexity didn't change between 26.2 and 26.3

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