[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/include/interface/transport.h

@@ -94,6 +94,7 @@ typedef uint32_t LG_TransportFrameFlags;
 
 typedef struct LG_TransportFrameTiming
 {
+  bool     valid; /* producer fields below are available and coherent */
   uint64_t captureTime;
   uint64_t postProcessTime;
   uint64_t copyTime;