Keep the Radio tuning dial silent unless a stream is playing

Releasing the tuning dial always started the chosen station, plus tuning
static, even when nothing was playing. It now follows the Previous/Next
rule: the release plays only if a stream was loading, buffering or playing
when the drag began; otherwise it just selects the station.

The privacy note no longer lists finishing tuning as a way to connect and
now names voice instead, in all locales. Docs, changelog and comments are
tightened to match.

changelog.d/1474-radio-next-no-autoplay.md

@@ -1,4 +1,5 @@
-- Radio Next and Previous no longer start a broadcaster stream before Play is
-  pressed; while a stream plays, it follows the new station. Play reads Pause
-  while a stream connects, and a tuner release onto a station the directory
-  dropped no longer leaves a Resume for another station (gekh, #1474).
+- Radio Next, Previous and the tuning dial no longer start a broadcaster stream
+  before Play is pressed; while a stream plays, it follows the new station.
+  Play reads Pause while a stream connects, and a tuner release onto a station
+  the directory removed or changed no longer leaves a Resume for another
+  station (gekh, #1474).