audioconvert: Always apply noise when asked

Rename empty.noise -> dither.noise and always add this amount of noise
when > 0. This also adds the noise to silent sounds, not only when
nothing is connected because that would also be a problem when an amp
needs to be kept alive with an non-0 signal.

Rename noise -> dither because we can use this also for dithering later.

See #705

src/daemon/client-rt.conf.in

@@ -90,5 +90,5 @@ stream.properties = {
     #channelmix.rear-delay = 12.0
     #channelmix.stereo-widen = 0.0
     #channelmix.hilbert-taps = 0
-    #empty.noise = 0
+    #dither.noise = 0
 }

src/daemon/client.conf.in

@@ -80,5 +80,5 @@ stream.properties = {
     #channelmix.rear-delay = 12.0
     #channelmix.stereo-widen = 0.0
     #channelmix.hilbert-taps = 0
-    #empty.noise = 0
+    #dither.noise = 0
 }

src/daemon/minimal.conf.in

@@ -212,7 +212,7 @@ context.objects = [
             #channelmix.stereo-widen = 0.0
             #channelmix.hilbert-taps = 0
             channelmix.disable     = true
-            #empty.noise = 0
+            #dither.noise = 0
             #node.param.Props      = {
             #    params = [
             #        audio.channels 6
@@ -274,7 +274,7 @@ context.objects = [
             #channelmix.stereo-widen = 0.0
             #channelmix.hilbert-taps = 0
             channelmix.disable     = true
-            #empty.noise = 0
+            #dither.noise = 0
             #node.param.Props      = {
             #    params = [
             #        audio.format  S16

src/daemon/pipewire-pulse.conf.in

@@ -66,7 +66,7 @@ stream.properties = {
     #channelmix.rear-delay = 12.0
     #channelmix.stereo-widen = 0.0
     #channelmix.hilbert-taps = 0
-    #empty.noise = 0
+    #dither.noise = 0
 }
 
 pulse.properties = {