Deprecate Anycast channels

Signed-off-by: Sahas Subramanian <sahas.subramanian@proton.me>

Author: shsms

src/frequenz/channels/_anycast.py

@@ -20,6 +20,12 @@
 _logger = logging.getLogger(__name__)
 
 
+@deprecated(
+    "Anycast channels are deprecated, because of the high cost of maintaining "
+    "something for which we don't have a use case. The implementation will "
+    "remain in the codebase in its current form at least until the next major "
+    "version."
+)
 class Anycast(Generic[ChannelMessageT]):
     """A channel that delivers each message to exactly one receiver.