docs/features: add missing extensions supported by various vulkan drivers

After noticing the extensions missing in !17767 (merged), I decided to check all of them, and found quite a few missing; far too many for me to make one commit for each with the appropriate Fixes: tag, so I just grouped them by driver.

Note to dozen, panvk, powervr: the last 3 commits are adding tracking of this information as you hadn't started doing so; I left those at the end in case you had a legitimate reason not to do it; in other words, I can easily drop these commits if you wish me to.

Note to lavapipe: in !8593 (merged) you added VK_KHR_display & VK_KHR_get_display_properties2 as supported in docs/features.txt, but src/gallium/frontends/lavapipe/lvp_device.c disagrees; I'll leave it to you guys to fix whichever one is wrong ;)
I removed these two from features.txt; see last commit.