feat(playout): configure device for alsa and pulseaudio system outputs (#2654)

### Description

Add hardware configuration to liquidsoap so that users may
set hardware output in config.yml.

---------

Co-authored-by: jo <ljonas@riseup.net>

playout/tests/liquidsoap/fixtures/__init__.py

@@ -92,6 +92,17 @@ TEST_STREAM_CONFIGS: List[Config] = [
             "system": [{"enabled": True, "kind": "pulseaudio"}],
         }
     ),
+    make_config_with_stream(
+        outputs={
+            "system": [
+                {
+                    "enabled": True,
+                    "kind": "pulseaudio",
+                    "device": "alsa_output.pci-0000_00_sink",
+                }
+            ],
+        }
+    ),
     make_config_with_stream(
         outputs={
             "system": [{"enabled": False, "kind": "alsa"}],