[Feature Request]: Support more builtin function

[domingozhang]

Is there an existing issue for the same feature request?

• [X] I have checked the existing issues.

Is your feature request related to a problem?

No response

Describe the feature you'd like

LEFT(str,len)

Returns the leftmost len characters from the string str, or NULL if any argument is NULL.

Sample: mysql> SELECT LEFT('foobarbar', 5); -> 'fooba'

Describe implementation you've considered

No response

Documentation, Adoption, Use Case, Migration Strategy

No response

Additional information

No response

[qingxinhome]

Support PR submission and merging of left system functions, including bvt test and unit test. Please know. @domingozhang @aressu1985 @daviszhen

[heni02]

@Ariznawlll test done，pr merged