Adds Lens Flare Sample KNI projects

[squarebananas]

Adds the Lens Flare Sample KNI projects for testing the occlusion query implementation on each platform.

Further PRs for adding/fixing OcclusionQuery support on Android & BlazorGL to follow.

In advance, the following adjustment has been made to LensFlareComponent.cs for handling GLES & WebGL differences:

// For GLES and WebGL occlusion queries, the exact pixel count is not available.
// Instead, a result of 1 indicates that one or more pixels are visible.
// Therefore the querySize (also used to calculate the occlusionAlpha value) is reduced accordingly.
if (GraphicsDevice.Adapter.Backend == GraphicsBackend.GLES
 || GraphicsDevice.Adapter.Backend == GraphicsBackend.WebGL)
    querySize = 1;