API Improvements (mostly around ImNui)

[bryanedds]

This release brings some breaking API changes that allow us to improve the usability and understandability of Nu's APIs, particularly ImNui. Detailed updates in change list below -

• Fixed non-usage of ReferenceEqualityComparer in PooledArray.
• Removed use of pooled collections since they are way to slow for what they're being used for.
• Optimized animation property updates.
• Updated doc comments to reflect change in BodyId type name.
• Exposed eye properties directly from World instance for common convenience.
• Renamed ImNui Recent functions to Declared for better understandability.
• Applied newly found algebraic pattern to Terra Firma.
• Closed semantic ImNui hole by assuming Gui as default group (ScreenDispatcher.CreateDefaultGroup method removed).

Full Changelog: v18.5.0...v18.6.0

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This discussion was created from the release API Improvements (mostly around ImNui).