[opt](string) optimize string equal comparision

[jacktengg]

Proposed changes

Issue Number: close #xxx

Problem summary

Optimize string equal and not-equal comparison by using memequal_small_allow_overflow15.

Checklist(Required)

• [ ] Does it affect the original behavior
• [ ] Has unit tests been added
• [ ] Has document been added or modified
• [ ] Does it need to update dependencies
• [ ] Is this PR support rollback (If NO, please explain WHY)

Further comments

If this is a relatively large or complex change, kick off the discussion at [email protected] by explaining why you chose the solution you did and what alternatives you considered, etc...

[jacktengg]

run buildall

[github-actions[bot]]

clang-tidy review says "All clean, LGTM! :+1:"

[jacktengg]

run buildall

[cambyzju]

Please give some performance result, before and after this pr.