Vulkan: integrate VK_EXT_swapchain_maintenance1

[floooh]

NOTE: not going to merge this since VK_EXT_swapchain_maintenance1 has too little support, not worth the hassle.

See: https://docs.vulkan.org/features/latest/features/proposals/VK_EXT_swapchain_maintenance1.html

Meh, I should have checked coverage before. Under 30% on Windows and under 40% on Linux isn't great :/

Let's just salvage the bugfixes and code cleanup, but abandon the rest:

• physical device selection fallthrough bug
• move swapchain image-view create/destroy into separate funcs
• _sapp_win32_update_dimensions() must not update framebuffer width/height
• _sapp_vk_recreate_swapchain() must fire resize event instead

Abandondend:

• deferred swapchain image allocation (reduces memory usage during resize)
• use immediate present mode on Windows during window resize/movement (less stuttery during movement, but still not as good as with DXGI on my NVIDIA PC)
• also fix an existing bug in physical device selection (would not properly error out when no suitable device was found)
• also fix existing bug where window-resizing would overwrite framebuffer width/height
• implement window system canvas scaling
  • NOTE: not supported on my Linux laptop, must be optional
  • to reduce resizing artefacts (black border)
  • to properly support high_dpi: false (render at half the canvas resolution)
• use new present-fence to properly recycle present-semaphores
  • ...does this allows to use a swapchain-image-count of 2 on Windows?