Fix #1055,DAYNAME() function in mysql mode not supported

[watchpoints]

What changes were proposed in this pull request?

https://github.com/oceanbase/oceanbase/issues/1055 add sys funciton
SELECT DAYNAME("2022-09-20")

Why are the changes needed?

myql

Will break the compatibility? How if so?

Does this PR introduce any user-facing change?

No

How was this patch tested?

Checklist

• [ ] I've run the tests to see all new and existing tests pass.