Update is_data_replica to include non-voting participants

Summary:
This change updates `is_data_replica/2` to correctly identify all participants that receive data replication, including both voting members and non-voting participants.

Previously, `is_data_replica/2` only checked the membership list (voting members: full members + witnesses), which excluded non-voting participants that also receive data replication. The function now checks the participants list instead, which includes all nodes that participate in the cluster.

The new implementation defines data replicas as all participants except witnesses, which correctly includes:
- Full members (voting + data replication)
- Non-voting participants (no voting + data replication)

While excluding witnesses (voting + no data replication).

This aligns with the RAFT configuration model where:
- Participants = all cluster nodes (voting members + non-voting participants)
- Membership = voting members only (full members + witnesses)
- Data replicas = participants that receive replication (participants - witnesses)

Reviewed By: hsun324

Differential Revision: D87658062

fbshipit-source-id: 17ad5b8ffc2a0facc660d0ee9c1e11412a1046fb

Author: Sarah Hassan

src/wa_raft_server.erl

@@ -389,18 +389,12 @@ get_config_witnesses(_) ->
     [].
 
 -spec is_data_replica(Identity :: #raft_identity{}, Config :: config() | config_all()) -> boolean().
-is_data_replica(#raft_identity{name = Name, node = Node}, #{version := 1, membership := Membership, witness := Witnesses}) ->
-    lists:member({Name, Node}, Membership) and not lists:member({Name, Node}, Witnesses);
-is_data_replica(#raft_identity{name = Name, node = Node}, #{version := 1, membership := Membership}) ->
-    lists:member({Name, Node}, Membership);
-is_data_replica(_, _) ->
-    false.
+is_data_replica(Identity, Config) ->
+    lists:member(Identity, get_config_participants(Config)) and not lists:member(Identity, get_config_witnesses(Config)).
 
 -spec is_witness(Identity :: #raft_identity{}, Config :: config() | config_all()) -> boolean().
-is_witness(#raft_identity{name = Name, node = Node}, #{version := 1, witness := Witnesses}) ->
-    lists:member({Name, Node}, Witnesses);
-is_witness(_, _) ->
-    false.
+is_witness(Identity, Config) ->
+    lists:member(Identity, get_config_witnesses(Config)).
 
 %% Create a new cluster configuration with no members.
 %% Without any members, this cluster configuration should not be used as