feat: v0.5.5 - enhanced priority fee system and dependency updates

- Update solana-streamer-sdk to 0.4.1
- Refactor priority fee API (custom_buy_tip_fee → custom_priority_fee)
- Simplify documentation and clean up examples

BREAKING CHANGE: priority fee parameter type changed

examples/middleware_system/src/main.rs

@@ -103,7 +103,6 @@ async fn test_middleware() -> AnyResult<()> {
             Box::new(PumpSwapParams::from_pool_address_by_rpc(&client.rpc, &pool_address).await?),
             None,
             true,
-            None,
         )
         .await?;
     println!("tip: This transaction will not succeed because we're using a test account. You can modify the code to initialize the payer with your own private key");