Release v0.4.5: More memory optimizations

• Improved the memory efficiency of load-time splat data optimizations
• Exposed internal optimizeSplatData parameter which controls whether or not splat data optimizations are performed. Defaults to true. Splat data optimizations will improve run-time performance, but require longer load times and increased memory overhead during scene load. They will be performed only if a scene is not progressively loaded.
• Changed plyInMemoryCompressionLevel to inMemoryCompressionLevel and applied it to all file types. Default is now 0 instead of 2.
• Added webXRSessionInit parameter for passing WebXR initialization options to the viewer (Thanks for the suggestion @arthurlebourg
• Added Viewer parameter to control scene reveal rate: sceneFadeInRateMultiplier. Default is 1.0.
• Added Viewer parameter to specify the precision for the distance map used in the splat sort algorithm: splatSortDistanceMapPrecision. Defaults to 16 (16-bit). Increasing this value is helpful for reducing sorting artifacts in scenes with large dimensions, but it will also decrease performance.
• Added function Viewer.setActiveSphericalHarmonicsDegrees() to set the spherical harmonics degree at run-time.
• Added SplatMesh.computeBoundingBox()
• Couple of bug fixes for ArrowHelper and fetchWithProgress() pointed out by @PeterZhizhin
• Fixed bug where viewer controls don't get disposed properly. Thanks @v2img for the heads up!
• Fixed progressive loading bug that caused a render of more splats than had been processed and resulted in visual artifacts.