Revert "zink: remove descriptor-mode selection infrastructure"

this would've been in-use, but khronos changes while I was on vacation
blocked a merge

This reverts commit 3f371d4e94.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/20489>

docs/drivers/zink.rst

@@ -249,6 +249,19 @@ are required to be supported
 
   * :ext:`VK_KHR_draw_indirect_count`
 
+Performance
+-----------
+
+If you notice poor performance and high CPU usage while running an application,
+changing the descriptor manager may improve performance:
+
+.. envvar:: ZINK_DESCRIPTORS <mode> ("auto")
+
+``auto``
+   Automatically detect best mode. This is the default.
+``lazy``
+   Attempt to use the least amount of CPU by binding descriptors opportunistically.
+
 Debugging
 ---------