Add lighthouse db command (#3129)

## Proposed Changes

Add a `lighthouse db` command with three initial subcommands:

- `lighthouse db version`: print the database schema version.
- `lighthouse db migrate --to N`: manually upgrade (or downgrade!) the database to a different version.
- `lighthouse db inspect --column C`: log the key and size in bytes of every value in a given `DBColumn`.

This PR lays the groundwork for other changes, namely:

- Mark's fast-deposit sync (https://github.com/sigp/lighthouse/pull/2915), for which I think we should implement a database downgrade (from v9 to v8).
- My `tree-states` work, which already implements a downgrade (v10 to v8).
- Standalone purge commands like `lighthouse db purge-dht` per https://github.com/sigp/lighthouse/issues/2824.

## Additional Info

I updated the `strum` crate to 0.24.0, which necessitated some changes in the network code to remove calls to deprecated methods.

Thanks to @winksaville for the motivation, and implementation work that I used as a source of inspiration (https://github.com/sigp/lighthouse/pull/2685).

beacon_node/lighthouse_network/src/peer_manager/mod.rs

@@ -388,7 +388,7 @@ impl<TSpec: EthSpec> PeerManager<TSpec> {
     /// Updates `PeerInfo` with `identify` information.
     pub fn identify(&mut self, peer_id: &PeerId, info: &IdentifyInfo) {
         if let Some(peer_info) = self.network_globals.peers.write().peer_info_mut(peer_id) {
-            let previous_kind = peer_info.client().kind.clone();
+            let previous_kind = peer_info.client().kind;
             let previous_listening_addresses =
                 peer_info.set_listening_addresses(info.listen_addrs.clone());
             peer_info.set_client(peerdb::client::Client::from_identify_info(info));
@@ -412,12 +412,9 @@ impl<TSpec: EthSpec> PeerManager<TSpec> {
                 ) {
                     metrics::inc_gauge_vec(
                         &metrics::PEERS_PER_CLIENT,
-                        &[&peer_info.client().kind.to_string()],
-                    );
-                    metrics::dec_gauge_vec(
-                        &metrics::PEERS_PER_CLIENT,
-                        &[&previous_kind.to_string()],
+                        &[peer_info.client().kind.as_ref()],
                     );
+                    metrics::dec_gauge_vec(&metrics::PEERS_PER_CLIENT, &[previous_kind.as_ref()]);
                 }
             }
         } else {
@@ -674,7 +671,7 @@ impl<TSpec: EthSpec> PeerManager<TSpec> {
             let value = clients_per_peer.get(&client_kind.to_string()).unwrap_or(&0);
             metrics::set_gauge_vec(
                 &metrics::PEERS_PER_CLIENT,
-                &[&client_kind.to_string()],
+                &[client_kind.as_ref()],
                 *value as i64,
             );
         }

beacon_node/lighthouse_network/src/peer_manager/peerdb/client.rs

@@ -4,7 +4,7 @@
 
 use libp2p::identify::IdentifyInfo;
 use serde::Serialize;
-use strum::{AsRefStr, AsStaticStr, EnumIter};
+use strum::{AsRefStr, EnumIter, IntoStaticStr};
 
 /// Various client and protocol information related to a node.
 #[derive(Clone, Debug, Serialize)]
@@ -21,7 +21,7 @@ pub struct Client {
     pub agent_string: Option<String>,
 }
 
-#[derive(Clone, Debug, Serialize, PartialEq, AsRefStr, AsStaticStr, EnumIter)]
+#[derive(Clone, Copy, Debug, Serialize, PartialEq, AsRefStr, IntoStaticStr, EnumIter)]
 pub enum ClientKind {
     /// A lighthouse node (the best kind).
     Lighthouse,