Fix diagnostics; set up CI which includes make run and cargo clippy

[zjp-CN]

This is a draft PR. I'll make it ready once the following problems are solved.

1. make BIN=loongarch64-qemu run leads to qemu-system-loongarch64: command not found (see CI ), so how to set up for loongarch64?
2. There are two clippy warnings left, but I'm not sure how to do

• for the first one, 01000 might be a typo, but what is it? 0x1000, 0o1000, or 0b1000?
• for the second one, parameter envp is not really used, so I think it can be removed?

 warning: this is a decimal constant
    --> kernel/src/syscall/shm.rs:35:21
     |
  35 |         if shmflg & 01000 > 0 {
     |                     ^^^^^
     |
     = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#zero_prefixed_literal
     = note: `#[warn(clippy::zero_prefixed_literal)]` on by default
  help: if you mean to use a decimal constant, remove the `0` to avoid confusion
     |
  35 |         if shmflg & 1000 > 0 {
     |                     ~~~~
  help: if you mean to use an octal constant, use `0o`
     |
  35 |         if shmflg & 0o1000 > 0 {
     |                     ~~~~~~

  warning: parameter is only used in recursion
     --> kernel/src/syscall/task.rs:191:5
      |
  191 |     envp: Vec<String>,
      |     ^^^^ help: if this is intentional, prefix it with an underscore: `_envp`
      |
  note: parameter used here
     --> kernel/src/syscall/task.rs:249:79
      |
  249 |             return exec_with_process(task, String::from("busybox"), new_args, envp).await;
      |                                                                               ^^^^
  ...
  272 |                 return exec_with_process(task, new_args[0].clone(), new_args, envp).await;
      |                                                                               ^^^^
      = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#only_used_in_recursion
      = note: `#[warn(clippy::only_used_in_recursion)]` on by default

3. KernelTask is undeclared with net feature enabled:

 error[E0433]: failed to resolve: use of undeclared type `KernelTask`
    --> kernel/src/tasks/mod.rs:89:25
     |
  89 |     thread::spawn_blank(KernelTask::new(handle_net()));
     |                         ^^^^^^^^^^ use of undeclared type `KernelTask`

4. Although there is a rust-toolchain.toml which specifies nightly-2023-12-01, the latest nightly toolchain is required somewhere and make run will fail (see CI ):

error: toolchain 'nightly-x86_64-unknown-linux-gnu' is not installed
Makefile:40: *** "ARCH" must be one of "x86_64", "riscv64", "aarch64" or "loongarch64".  Stop.