refactor(gas-fee): replace init_builtin_fee_strategies with set_global_strategy

- Add customizable cu_limit, cu_price, buy_tip, sell_tip parameters
- Update all examples and documentation
- Simplify strategy configuration API

examples/nonce_cache/src/main.rs

@@ -105,8 +105,8 @@ async fn create_solana_trade_client() -> AnyResult<SolanaTrade> {
     let swqos_configs: Vec<SwqosConfig> = vec![SwqosConfig::Default(rpc_url.clone())];
     let trade_config = TradeConfig::new(rpc_url, swqos_configs, commitment);
     let solana_trade = SolanaTrade::new(Arc::new(payer), trade_config).await;
-    // init gas fee strategy
-    sol_trade_sdk::common::GasFeeStrategy::init_builtin_fee_strategies();
+    // set global strategy
+    sol_trade_sdk::common::set_global_gas_fee_strategy(150000, 500000, 0.001, 0.001);
     println!("✅ SolanaTrade client initialized successfully!");
     Ok(solana_trade)
 }