Implement native function of dayofweek.

[weimingdiit]

Description
Implement Spark-compatible dayofweek() function

Auron already supports several Spark-compatible date/time extraction functions such as year(), month(), dayofmonth(), quarter(), hour(), minute(), and second().
However, Spark also provides a companion function dayofweek() that returns the day of the week using Spark’s semantics:

Sunday = 1, Monday = 2, ..., Saturday = 7

To improve compatibility with Spark SQL, we should implement dayofweek() natively with the following characteristics:

Expected behavior

Function name: dayofweek(expr)
Return type: INT
Semantics: Sunday = 1, Monday = 2, ..., Saturday = 7
Example:

dayofweek('2009-07-30') → 5

Supports: DATE, TIMESTAMP, and compatible string/date inputs consistent with existing date extraction functions

Null-safe: should return NULL if input is NULL
Array and scalar inputs: consistent with current date extraction function implementations

Motivation
Ensure feature parity with Apache Spark SQL
Improve compatibility for expressions and queries migrated from Spark
Reduce fallback occurrences to Spark expression/UDF wrapper