All the fields of FFVkCodecMap are either decoder-only
or encoder-only (with the latter being unused and unset for now).
Yet there is already a per-decoder struct containing
static information about these decoders, namely
VkExtensionProperties.
This commit merges the decoder-parts of FFVkCodecMap
with the VkExtensionProperties into a common structure.
Given that FFVkCodecMap is now unused, it is removed.
Reviewed-by: Lynne <dev@lynne.ee>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>