glx: fix querying GLX_FBCONFIG_ID for Window

glx: fix querying GLX_FBCONFIG_ID for Window

This commit fixes apps using the following sequence:
1. XCreateWindow(dpy) -> win
2. glXCreateContextAttribsARB(dpy, ...) -> ctx
3. glXMakeCurrent(dpy, win, ctx)
4. glXQueryDrawable(dpy, win, GLX_FBCONFIG_ID, ...)

glXQueryDrawable returned 0 (while correctly returning a valid
GLXFCONFIG_ID for other types of drawables).

This commit adds the same dance as driInferDrawableConfig to get
the GLX visual from the Window, and then the GLXFBCONFIG_ID of
this visual.

This fixes:
* piglit: glx-query-drawable --attr=GLX_FBCONFIG_ID --type=WINDOW
* Maya which uses the config ID from step 4 as an input to
glXChooseFBConfig.

Reviewed-by: Adam Jackson <ajax@redhat.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/14174>