update gitignore for enhanced kernel

[Okabe-Rintarou-0]

What type of PR is this?
cleanup

What this PR does / why we need it:
update gitignore for enhanced kernel. When using enhanced kernel, we will generate these files:

Which issue(s) this PR fixes:

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 49.25%. Comparing base (18b35d4) to head (a30c819).
Report is 5 commits behind head on main.

see 2 files with indirect coverage changes

---

Continue to review full report in Codecov by Sentry.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 8dce347...a30c819. Read the comment docs.

[hzxuzhonghu]

/lgtm

This is a good improvement for developers

[kmesh-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: hzxuzhonghu

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [hzxuzhonghu]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment