Software Renderer is missing Affine/Geometry palleted to RGB blits #14419
Description
I first noticed this when I viewed the Emscripten builds of the affine-textures and geometry examples in a Firefox browser fork that disables WebGL for some privacy/security reason. In that context SDL fallsback to the Software Renderer and renderers the sample.png bitmap image as all white for any case that the geometry render command is used. This can also be seen when the SDL_RENDER_DRIVER=software hint is set.
I've traced this back to commit 0b4b254 and to confirm that is was due to the introduction of paletted rendering, I tried converting sample.png (which is a paletted bitmap) to RGB and saw the Software Renderer work correctly with the RGB Surface/Texture.
I have not checked if rendering to paletted textures works or doesn't with any renderer driver.