Require all feature flags introduced before 3.11.1

RabbitMQ 3.12 requires feature flag feature_flags_v2 which got
introduced in 3.11.0 (see
#6810).

Therefore, we can mark all feature flags that got introduced in 3.11.0
or before 3.11.0 as required because users will have to upgrade to
3.11.x first, before upgrading to 3.12.x

The advantage of marking these feature flags as required is that we can
start deleting any compatibliy code for these feature flags, similarly
as done in #5215

This list shows when a given feature flag was first introduced:

classic_mirrored_queue_version 3.11.0
stream_single_active_consumer 3.11.0
direct_exchange_routing_v2 3.11.0
listener_records_in_ets 3.11.0
tracking_records_in_ets 3.11.0

empty_basic_get_metric 3.8.10
drop_unroutable_metric 3.8.10

Author: ansd

deps/rabbit/src/rabbit_core_ff.erl

@@ -20,7 +20,8 @@
 -rabbit_feature_flag(
    {classic_mirrored_queue_version,
     #{desc          => "Support setting version for classic mirrored queues",
-      stability     => stable
+      %%TODO remove compatibility code
+      stability     => required
      }}).
 
 -rabbit_feature_flag(
@@ -68,7 +69,8 @@
    {stream_single_active_consumer,
     #{desc          => "Single active consumer for streams",
       doc_url       => "https://www.rabbitmq.com/stream.html",
-      stability     => stable,
+      %%TODO remove compatibility code
+      stability     => required,
       depends_on    => [stream_queue]
      }}).
 
@@ -81,15 +83,17 @@
 -rabbit_feature_flag(
    {direct_exchange_routing_v2,
     #{desc       => "v2 direct exchange routing implementation",
-      stability  => stable,
+      %%TODO remove compatibility code
+      stability  => required,
       depends_on => [feature_flags_v2, implicit_default_bindings],
       callbacks  => #{enable => {?MODULE, direct_exchange_routing_v2_enable}}
      }}).
 
 -rabbit_feature_flag(
    {listener_records_in_ets,
     #{desc       => "Store listener records in ETS instead of Mnesia",
-      stability  => stable,
+      %%TODO remove compatibility code
+      stability  => required,
       depends_on => [feature_flags_v2],
       callbacks  => #{enable =>
                       {?MODULE, listener_records_in_ets_enable},
@@ -100,7 +104,8 @@
 -rabbit_feature_flag(
    {tracking_records_in_ets,
     #{desc          => "Store tracking records in ETS instead of Mnesia",
-      stability     => stable,
+      %%TODO remove compatibility code
+      stability     => required,
       depends_on    => [feature_flags_v2],
       callbacks     => #{enable =>
                              {?MODULE, tracking_records_in_ets_enable},

deps/rabbitmq_management_agent/src/rabbit_mgmt_ff.erl

@@ -10,11 +10,13 @@
 -rabbit_feature_flag(
    {empty_basic_get_metric,
     #{desc          => "Count AMQP `basic.get` on empty queues in stats",
-      stability     => stable
+      %%TODO remove compatibility code
+      stability     => required
      }}).
 
 -rabbit_feature_flag(
   {drop_unroutable_metric,
    #{desc          => "Count unroutable publishes to be dropped in stats",
-     stability     => stable
+     %%TODO remove compatibility code
+     stability     => required
     }}).