Implement kill system call

[bayedieng]

This pr implements the kill syscall in order to further linux compatibility, omitting permission checks as Linux capabilities need to be implemented to do so.

Pre-Submission Checklist

When you submit a PR, please make sure your PR satisfies the following checklist:

• I assert this contribution was authored by me.
• I license this contribution under the license of this project.
• The PR title describes your changes briefly and uses the present tense, without a trailing full stop.
• The PR description describes the reason why we need the change.
• This is an isolated change. No multiple changes and no unrelated changes are included.
• Fixed all cargo clippy warnings.
• Applied rustfmt.

[nuta]

Thanks for the PR! Could you restore the submission checklist in the PR description?

[nuta]

@bayedieng I can't see any fixes for my comments. Perhaps did you forget to push commits?

[bayedieng]

@nuta updated.

[nuta]

Thanks for the update! I have few minor review comments:

[nuta]

Thanks @bayedieng!