Update oscamp to support x86_64.

[MTttth]

Update Toolchain and Add x86_64 Support

• Update rust-toolchain to nightly-2025-05-20
• Fix critical bugs in arch/x86_64/context.rs and trap.rs. Enable x86_64 support in context switching and trap handling
• Successfully run u_*_0 apps on x86_64
• Still panic in m_*_ apps, likely due to disk.img issues

Details

x86_64 Context and Trap Fixes

• Corrected register save/restore logic in context.rs
• Improved trap frame setup for syscall and interrupt handling
• Verified context switching on x86_64

App Execution

• Kernel panics when running m_*_ apps, appears during FAT filesystem mounting or app loading
• Suspected issue in how disk.img is constructed for x86_64

TODO

• Fix bugs in m_*_
• Add CI testing for x86_64 builds and QEMU runs