refactor: Replace global address lookup table cache with direct fetch approach

Replace the global AddressLookupTableCache with a direct fetch function to simplify address lookup table management. This change improves code maintainability by removing global state and makes the API more explicit.

Key changes:
- Remove AddressLookupTableCache and AddressLookupManager
- Add new fetch_address_lookup_table_account function
- Update TradeBuyParams and TradeSellParams to use AddressLookupTableAccount instead of Pubkey
- Update all examples to use the new direct fetch approach
- Update documentation to reflect the simplified workflow

examples/pumpswap_trading/src/main.rs

@@ -194,7 +194,7 @@ async fn pumpswap_trade_with_grpc(mint_pubkey: Pubkey, params: PumpSwapParams) -
         slippage_basis_points: slippage_basis_points,
         recent_blockhash: Some(recent_blockhash),
         extension_params: Box::new(params.clone()),
-        lookup_table_key: None,
+        address_lookup_table_account: None,
         wait_transaction_confirmed: true,
         create_input_token_ata: true,
         close_input_token_ata: true,
@@ -227,7 +227,7 @@ async fn pumpswap_trade_with_grpc(mint_pubkey: Pubkey, params: PumpSwapParams) -
         recent_blockhash: Some(recent_blockhash),
         with_tip: false,
         extension_params: Box::new(params.clone()),
-        lookup_table_key: None,
+        address_lookup_table_account: None,
         wait_transaction_confirmed: true,
         create_output_token_ata: true,
         close_output_token_ata: true,