Supporting running kernel mode unit test in kernel threads

[grief8]

This pull request enhances the execution of ktests within a task-based context by performing the following steps:

1. Introducing a straightforward FIFO Scheduler to manage task execution sequence.
2. Incorporating the run_ktests function into the task context.
3. Integrating the ktests specific to Task within this pull request for comprehensive functionality.

The development of capabilities to facilitate the concurrent execution of multiple ktest tasks is still an ongoing effort. Despite Asterinas currently only supporting a single core, the parallelization of unit tests is a more logical approach, promising improved efficiency and performance. This feature will involve a lot of code in libs/ktest and requires further discussion.

[tatetian]

This is an important missing feature of the ktest mechanism. Very excited to see this PR. I skimmed over the changes. Looks fine to me.

@junyang-zh As the author of ktest, your opinion would be highly appreciated.

[junyang-zh]

Yes this is just the first step to run ktests in parallel. If you are uninterested in implementing the following features, I am OK to take and I am OK with the scope of this PR.

[grief8]

Yes this is just the first step to run ktests in parallel. If you are uninterested in implementing the following features, I am OK to take and I am OK with the scope of this PR.

Considering that we currently do not support multi-threading and cannot conduct complete testing even after implementation, I think the current PR should be enough.

[tatetian]

LGTM. Thanks for contribution!