Migrate validator client to clap derive (#6300)

Partially #5900


  Migrate the validator client cli to clap derive

validator_client/beacon_node_fallback/Cargo.toml

@@ -9,6 +9,7 @@ name = "beacon_node_fallback"
 path = "src/lib.rs"
 
 [dependencies]
+clap = { workspace = true }
 environment = { workspace = true }
 eth2 = { workspace = true }
 futures = { workspace = true }