Fix: Tests: Two-stage shader compilation in EEVEE performance tests

The EEVEE performance tests wait for shader compilation to finish before
beginning to record performance. However, shader compilation can also
happen after the first frame. This PR adds a check to the warmup phase
to see if shader compilation is still happening. This happens, e.g., for
the Mr. Elephant demo scene.

Pull Request: https://projects.blender.org/blender/blender/pulls/143690

tests/performance/tests/eevee.py

@@ -72,7 +72,10 @@ def frame_change_handler(scene):
 
     elif record_stage == RecordStage.WARMUP:
         warmup_frame += 1
-        if time.perf_counter() - start_warmup_time > WARMUP_SECONDS and warmup_frame > WARMUP_FRAMES:
+        # Check for two-stage shader compilation that can happen later than the first frame.
+        if hasattr(bpy.app, 'is_job_running') and bpy.app.is_job_running("SHADER_COMPILATION"):
+            record_stage = RecordStage.WAIT_SHADERS
+        elif time.perf_counter() - start_warmup_time > WARMUP_SECONDS and warmup_frame > WARMUP_FRAMES:
             start_record_time = time.perf_counter()
             playback_iteration = 0
             num_frames = 0