Simpler non point sprites perflevel

Windows d3d11 doesn't support point sprite sizes (d3d11 QRhi::VertexShaderPointSize returns false). Because of this, lowest available particles PerformanceLevel on d3d11 is Deformable, even with simpler particles which would need only features of Simple or Colored.

Consider implementing one more alternative vertex data & shader level which would be like Colored but use DrawTriangles instead of DrawPoints. This would reduce the memory usage and improve the performance due to simpler shader.