[SPARK-58044][SQL] Support the TIME data type in the aggregate function avg

[marcuslin123]

What changes were proposed in this pull request?

Add TimeType support to the avg/mean aggregate function. Previously AVG() only accepted numeric and ANSI interval types and rejected TIME. Since TIME is internally a Long number of nanoseconds since midnight, it can be averaged like the interval types.

SELECT avg(t) FROM VALUES (TIME'10:00:00'), (TIME'14:00:00') AS tab(t);
-- 12:00:00

The changes:

• Average.scala: accept AnyTimeType in inputTypes; map a TIME input to a TIME output of the same precision in resultType; accumulate the sum as LongType; and add a TIME branch to evaluateExpression that divides the summed nanoseconds by the count and re-tags the result as TimeType(precision).
• To accumulate the sum, the child value is converted to the sum's type via PreciseTimestampConversion rather than a regular cast. A regular CAST(time AS BIGINT) is lossy for this purpose — it truncates to whole seconds — so it would corrupt the average. PreciseTimestampConversion reinterprets the underlying Long nanoseconds without changing the value.
• New TimeDivide expression (in intervalExpressions.scala, modeled on DivideDTInterval) that divides a Long-nanosecond sum by the count with HALF_UP rounding and returns a TimeType(precision). DivideDTInterval could not be reused because its output type is hardcoded to DayTimeIntervalType, and there is no CAST(BIGINT AS TIME) to re-wrap the result.
• New TypeUtils.checkForAnsiIntervalOrNumericOrTimeType helper. Sum's existing checkForAnsiIntervalOrNumericType is intentionally left unchanged, since Sum does not (yet) support TIME.

The output preserves the input precision (e.g. avg over a TIME(3) column yields TIME(3)). This mirrors how min/max/percentile already support TIME.

Why are the changes needed?

TIME is orderable and quantifiable, and min, max, percentile, approx_percentile, etc. already support it. avg was an inconsistent gap: to average a TIME column, users had to cast to a numeric type, average, and cast back. Native support lets them write avg(time_col) directly.

Does this PR introduce any user-facing change?

Yes. avg/mean now accepts TIME columns and returns a TIME average (same precision). Previously it raised a DATATYPE_MISMATCH.UNEXPECTED_INPUT_TYPE error.

How was this patch tested?

Added a test in DataFrameAggregateSuite covering: basic average, sub-second rounding, NULL handling, all-null/empty input (returns NULL), precision preservation (TIME(3)), grouped average, and the SQL avg surface over TIME literals. Updated the expected error message in ExpressionTypeCheckingSuite (avg's required-type list now includes TIME). Full DataFrameAggregateSuite (168 tests) passes with no regressions, including the existing interval-avg test.

Was this patch authored or co-authored using generative AI tooling?

Generative AI tooling (Claude Code) was used as an assistive tool for implementation guidance.