Vulkan: Re-enable Mesa device select layer

We got this from RenderDoc which had an issue with it 5 years ago, but it's
not a given that Godot is also affected.

This layer is actually quite convenient to be able to change what default Vulkan
capable GPU should be used for applications via environment variables:
https://docs.mesa3d.org/envvars.html#vulkan-mesa-device-select-layer-environment-variables

(cherry picked from commit c9f0ab67015f1a88d87de634c1c62119b79ecc00)

main/main.cpp

@@ -2522,7 +2522,7 @@ Error Main::setup(const char *execpath, int argc, char *argv[], bool p_second_ph
 			"DISABLE_SAMPLE_LAYER", // GH-104154.
 			"DISABLE_GAMEPP_LAYER", // GH-104154.
 			"DISABLE_VK_LAYER_TENCENT_wegame_cross_overlay_1", // GH-104154.
-			"NODEVICE_SELECT", // GH-104154.
+			// "NODEVICE_SELECT", // Kept as it's useful - GH-104592.
 			"VK_LAYER_bandicam_helper_DEBUG_1", // GH-101480.
 			"DISABLE_VK_LAYER_bandicam_helper_1", // GH-101480.
 			"DISABLE_VK_LAYER_reshade_1", // GH-70849.