feat: Support --arch and --nobios options

[Ivans-11]

Add --arch and --nobios flags to support RISC-V 32/64 architecture selection and no-BIOS mode.

# RV64 SBI mode (default)
cargo qemu --ch x

# RV64 nobios mode
cargo qemu --ch x --nobios

# RV32 nobios mode (RV32 only supports nobios)
cargo qemu --ch x --arch riscv32 --nobios