samples: bluetooth: locator_tag: Move speaker handling to LED thread

Move speaker handling to a LED thread, now called indication thread.
The signaling of the indications is accomplished by using k_event API.
The events are used to signal the button and ringing indications.

On platforms with a speaker during ringing and button presses
the speaker makes a sound synchronously with a LED indication.

Fixed dropping the ringing status indication during
the motion detection event.

Jira: NCSDK-38277

Signed-off-by: Dominik Chat <dominik.chat@nordicsemi.no>

Author: dchat-nordic

doc/nrf/releases_and_maturity/releases/release-notes-changelog.rst

@@ -340,6 +340,14 @@ Bluetooth Fast Pair samples
 
   Support for this target was already dropped during the IronSide SE migration in the |NCS| v3.1.0 release.
 
+* :ref:`fast_pair_locator_tag` sample:
+
+  * Updated the UI thread handling for reference board targets with a speaker by moving the speaker control into the common indication thread.
+    The signaling is now done using the :ref:`zephyr:events` API.
+
+  * Fixed the ringing status indications with the green LED flashes for reference board targets.
+    A ringing status indication was often skipped during the motion detection event.
+
 Cellular samples
 ----------------