feat: exec args & envs

[AsakuraMizu]

This PR mainly adds support for args and envs for exec. Additionally, several issues closely related to exec have been fixed:

1. Testcases should run in the same directory as the executable
2. libc.so path should be absolute
3. clone_task should set user heap base
4. current_task.set_name should not reference data in the old user space
5. MutexGuard<AddrSpace> should be dropped before entering user space

[Azure-stars]

If you can pass exec test case, please refer to readme to add it to testcases list for CI test.

You can submit changes after ensuring that the local test passes.

[AsakuraMizu]

If you can pass exec test case, please refer to readme to add it to testcases list for CI test.

You can submit changes after ensuring that the local test passes.

I could not pass the test as the test script doesn't handle line endings when comparing two strings. I think maybe we could improve the test script elsewhere and let this PR just focus on exec.

[Azure-stars]

If you can pass exec test case, please refer to readme to add it to testcases list for CI test.
You can submit changes after ensuring that the local test passes.

I could not pass the test as the test script doesn't handle line endings when comparing two strings. I think maybe we could improve the test script elsewhere and let this PR just focus on exec.

Fix it on 52b0ed9