privileges: add missing items for show privileges | tidb-test=pr/2067 (#40600)

[ti-chi-bot]

This is an automated cherry-pick of #40600

What problem does this PR solve?

Issue Number: close #40591

Problem Summary:

Now the result of show privileges misses 3 ones: CONFIG, Create role, and Drop role.

[ti-chi-bot]

[REVIEW NOTIFICATION]

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• CbcWestwolf
• xhebox

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[xhebox]

/merge

[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: 5e1db24

[ti-chi-bot]

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