Improve UX when falling back between Display Servers

[Riteo]

The current UX for DS fallbacks is a bit confusing, as there's quite a bit of (possibly unrelated) errors and then a working game:

Example log from X11 to Wayland

$ DISPLAY=/dev/null bin/godot.linuxbsd.editor.dev.x86_64 --display-driver x11 --rendering-driver opengl3
Godot Engine v4.3.dev.custom_build.1313cd90a (2024-05-09 09:51:35 UTC) - https://godotengine.org
Error loading shared library libXinerama.so.1: No such file or directory
ERROR: X11 Display is not available
   at: DisplayServerX11 (platform/linuxbsd/x11/display_server_x11.cpp:5861)
Your video card drivers seem not to support the required OpenGL 3.3 version.

If possible, consider updating your video card drivers.

If you recently updated your video card drivers, try rebooting.
Plugin "GTK3 plugin" uses conflicting symbol "png_free".
Error loading shared library libspeechd.so.2: No such file or directory
Invalid value (0) for DRI_PRIME. Should be > 0
Inconsistent value (1) for DRI_PRIME. Should be < 1 (GPU devices count). Using: 0
Inconsistent value (2) for DRI_PRIME. Should be < 1 (GPU devices count). Using: 0
Inconsistent value (3) for DRI_PRIME. Should be < 1 (GPU devices count). Using: 0
OpenGL API 4.6 (Core Profile) Mesa 23.3.5 - Compatibility - Using Device: AMD - AMD Radeon Vega 8 Graphics (radeonsi, raven, LLVM 17.0.6, DRM 3.57, 6.8.8)

This patchset¹ aims to improve the situation where possible, without introducing any big change yet:

• From core, we display a warning whenever a fallback is being attempted;

• From X11, we alert the user about a failed rendering driver initialization only if it was actually attempted;

• From Wayland we actually implement the aforementioned alerts, as they were missing (oops).

New log when falling back from X11 to Wayland

$ DISPLAY=/dev/null bin/godot.linuxbsd.editor.dev.x86_64 --display-driver x11 --rendering-driver opengl3
Godot Engine v4.3.dev.custom_build.1313cd90a (2024-05-09 09:51:35 UTC) - https://godotengine.org
Error loading shared library libXinerama.so.1: No such file or directory
ERROR: X11 Display is not available
   at: DisplayServerX11 (platform/linuxbsd/x11/display_server_x11.cpp:5842)
WARNING: Display driver x11 failed, falling back to wayland.
     at: setup2 (main/main.cpp:2701)
Plugin "GTK3 plugin" uses conflicting symbol "png_free".
Error loading shared library libspeechd.so.2: No such file or directory
Invalid value (0) for DRI_PRIME. Should be > 0
Inconsistent value (1) for DRI_PRIME. Should be < 1 (GPU devices count). Using: 0
Inconsistent value (2) for DRI_PRIME. Should be < 1 (GPU devices count). Using: 0
Inconsistent value (3) for DRI_PRIME. Should be < 1 (GPU devices count). Using: 0
OpenGL API 4.6 (Core Profile) Mesa 23.3.5 - Compatibility - Using Device: AMD - AMD Radeon Vega 8 Graphics (radeonsi, raven, LLVM 17.0.6, DRM 3.57, 6.8.8)

It's not perfect by any means (the DRI_PRIME stuff is especially annoying), but those were some fairly low-hanging fruits and so this will do in the meantime.

Footnotes

1. Yes, sorry for making three commits but they feel all equally sensitive and unrelated. Please tell me if a single squashed commit is preferred. ↩

[Riteo]

All right I implemented all the suggestions and added an extra EGLManager::open_display check for the GLES driver, in order to make it fail properly if we can't actually open a display instead of failling when creating a window.