Using swapchain in bevy render graph

[blaind]

OpenXR runtime reports the possible swapchain texture format (see https://github.com/blaind/bevy_openxr/blob/e48bd27130cfb3b735edf2d6ce6355bb5c2490f0/crates/bevy_openxr_core/src/swapchain.rs#L100).

The same format should be used in bevy render graph in order not to lose precision during conversions.

At least repos\bevy\crates\bevy_pbr\src\render_graph\pbr_pipeline\mod.rs should be configured.

Maybe window creation flow can be used? Since swapchain is configured late in the process. Alternatively, texture formats could be enumerated immediately after the openxr session has been created.

could look at the window creation flow to figure out how to do this. The normal graphics context is also created after the window is, and this is in a way a similar flow. Alternatively look at the multiple window example, that deals with late creation of windows and the swapchain for that.