Have a resource path => vkShaderModule hash table instead of doing fancy
custom objects.
A benefit is that shader modules are now shared between all renderers
and pipelines.
Make the display handle the cache, because we only need one.
We store the cache in
$CACHE_DIR/gtk-4.0/vulkan-pipeline-cache/$UUID.$VERSION
so we regenerate caches for each different device (different UUID) and
each different driver version.
We also keep track of the etag of the cache file, so if 2 different
applications update the cache, we can detect that.
Vulkan allows merging caches, so the 2nd app reloads the new cache file
and merges it into its cache before saving.
As far as possible, use per-display debug flags.
This will minimize the debug spew that we get from
the inspector if it is running on a separate display.
Previously, code would work fine with --disable-vulkan if the Vulkan
headers were installed - code would happily just use them as they're
installed in /usr/include.
gdk_window_create_vulkan_context() now exists and will return a Vulkan
context for the given window. It even initializes the surface. But it
doesn't do anything useful yet.
Adds the gdk_display_ref_vulkan() and gdk_display_unref_vulkan()
functions which setup/tear down VUlkan support for the display.
Nothing is using those functions yet.
