- Refactor the [repo](https://github.com/aoooos/arceos) code to merge
- Use standard toolchain
- Fix the compile command

1. Use r21 register to record percpu variable address
2. Add page table description, although la64 does not use page table for
   the time being.
3. Modify the kernel page table remap part in runtime. la64 does not
   require remapping.

This commit includes multiple changes aimed at ensuring all apps/task and fs can be supported properly. These edits affect various files within the 'axhal' module and its subdirectories, as well as specific system configuration aspects outlined in the 'loongarch64-qemu-virt.toml' file.

fix bugs about percpu, use r21 register;
fix bugs about timer interrupt;
Simplify saving and restoring trap context;

Since loongarch64 does not seem to have the musl tool chain, here we use
the gnu tool chain.

1. add pointer type definition
2. add float definition
3. add setjmp/longjmp

rename loongArch64 to loongarch64

Remove unnecessary firmware programs and add help documentation.

Rewrite boot code.
Add pci address space definition
Fix word errors for platforms/*.toml