built-in-function: Support returning a null instead of returning zero when data/time functions come across with an exception

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OpenMLDB have a lots of date/time built-in functions. For example, we provides functions like 'dayofyear()', `dayofweek()`, etc.
We would like to return a NULL value when an exception occurs during parse a date or time.\

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Look for date/time built-in functions like dayofyear() and dayofweek() in the codebase, likely in a directory like src/builtin or similar. Understand how exceptions are currently handled and where NULL returns can be inserted. Check existing tests for these functions to see the expected behavior and add new test cases for exception scenarios.

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