[client] expose EGL stages in frame latency

Correlate received frames with the texture update actually consumed by
the renderer and retain damage until its token becomes renderable.

Split client latency into dispatch, import, queue, preparation, setup,
effects, desktop, composition, and swap stages in FRAME LATENCY.
Exclude diagnostic overlay work from composition and preserve client
wait time when producer timing is unavailable.

Publish joined samples through a bounded token queue, avoid sleeping
while producer timing is finalized, and correct Wayland photon units.

client/renderers/EGL/damage.h

@@ -27,8 +27,9 @@
 
 struct DesktopDamage
 {
-  int count;
-  FrameDamageRect rects[LG_MAX_FRAME_DAMAGE_RECTS];
+  LG_RendererFrameToken frameToken;
+  int                   count;
+  FrameDamageRect       rects[LG_MAX_FRAME_DAMAGE_RECTS];
 };
 
 typedef struct EGL_Damage EGL_Damage;