c/consensus_utils: adjust recovery offset ranges

For cloud based recovery, once segments are downloaded, the state for
raft, kvstore and local storage needs to be updated to reflect the
recovered log. Previously, the offsets were slightly off and this commit
adjusts them to always refer to the first/last offsets in the log.

src/v/raft/consensus_utils.cc

@@ -514,11 +514,11 @@ ss::future<> create_offset_translator_state_for_pre_existing_partition(
       raftlog.debug,
       "{} Set highest_known_offset in kv-store to {}",
       ntp_cfg.ntp(),
-      get_prev_offset(max_rp_offset));
+      max_rp_offset);
     co_await api.kvs().put(
       storage::kvstore::key_space::offset_translator,
       raft::offset_translator::kvstore_highest_known_offset_key(group),
-      reflection::to_iobuf(get_prev_offset(max_rp_offset)));
+      reflection::to_iobuf(max_rp_offset));
 }
 
 ss::future<> create_raft_state_for_pre_existing_partition(
@@ -534,18 +534,21 @@ ss::future<> create_raft_state_for_pre_existing_partition(
       raftlog.debug,
       "{} Prepare raft state, set latest_known_offset {} to the kv-store",
       ntp_cfg.ntp(),
-      get_prev_offset(max_rp_offset));
+      max_rp_offset);
     auto key = raft::details::serialize_group_key(
       group, raft::metadata_key::config_latest_known_offset);
     co_await api.kvs().put(
       storage::kvstore::key_space::consensus,
       key,
-      reflection::to_iobuf(get_prev_offset(max_rp_offset)));
+      reflection::to_iobuf(max_rp_offset));
 
     // Prepare Raft snapshot
     raft::group_configuration group_config(
       initial_nodes, ntp_cfg.get_revision());
     raft::snapshot_metadata meta = {
+      // `last_included_index` should be the last offset included in
+      // this fake snapshot. That's why we set it to be the first offest
+      // before the start of the recovered log.
       .last_included_index = get_prev_offset(min_rp_offset),
       .last_included_term = last_included_term,
       .version = raft::snapshot_metadata::current_version,