perf: ALSA ffmpeg low-delay flags

nobuffer, low_delay, and a small thread_queue_size on the camera
mic capture process.

tests/test_run_worker_ffmpeg.py

@@ -0,0 +1,10 @@
+import inspect
+
+import run_worker
+
+
+def test_alsa_ffmpeg_uses_low_delay_flags():
+    src = inspect.getsource(run_worker)
+    assert '"-fflags", "nobuffer"' in src
+    assert '"-flags", "low_delay"' in src
+    assert '"-thread_queue_size", "64"' in src