fix: instruction fault

Convert user_lib print functions to proper macros:

• Add Stdout struct implementing core::fmt::Write
• Implement print! and println! macros with format_args! support
• Update all user programs to use macro syntax (println! instead of println)
• Add macro_test.rs to demonstrate formatting capabilities

Features:

• Full format string support: println!("x={}, y={}", x, y)
• Hex formatting: println!("0x{:x}", value)
• Expression evaluation: println!("result: {}", 5 * 6)
• Compatible with standard Rust formatting

All user programs updated:

• 00poweroff.rs, 01hello.rs: Basic string output
• power_3/5/7.rs, test_simple.rs: Number formatting with {}
• macro_test.rs: Comprehensive formatting examples