fix: Convert vendor/pezkuwi-subxt from submodule to regular directory

vendor/pezkuwi-subxt/subxt/examples/setup_rpc_chainhead_backend.rs

@@ -0,0 +1,35 @@
+//! Example to utilize the ChainHeadBackend rpc backend to subscribe to finalized blocks.
+
+#![allow(missing_docs)]
+
+use futures::StreamExt;
+use subxt::backend::chain_head::{ChainHeadBackend, ChainHeadBackendBuilder};
+use subxt::backend::rpc::RpcClient;
+use subxt::{OnlineClient, PolkadotConfig};
+
+// Generate an interface that we can use from the node's metadata.
+#[subxt::subxt(runtime_metadata_path = "../artifacts/polkadot_metadata_small.scale")]
+pub mod polkadot {}
+
+#[tokio::main]
+async fn main() -> Result<(), Box<dyn std::error::Error>> {
+    tracing_subscriber::fmt::init();
+
+    let rpc = RpcClient::from_url("ws://localhost:9944".to_string()).await?;
+    let backend: ChainHeadBackend<PolkadotConfig> =
+        ChainHeadBackendBuilder::default().build_with_background_driver(rpc.clone());
+    let api = OnlineClient::from_backend(std::sync::Arc::new(backend)).await?;
+
+    let mut blocks_sub = api.blocks().subscribe_finalized().await?.take(100);
+
+    while let Some(block) = blocks_sub.next().await {
+        let block = block?;
+
+        let block_number = block.number();
+        let block_hash = block.hash();
+
+        println!("Block #{block_number} ({block_hash})");
+    }
+
+    Ok(())
+}