feat: add array_sum, array_product, array_avg functions and list_min alias

[crm26]

Which issue does this PR close?

Closes gaps in DataFusion's array function coverage compared to DuckDB (list_sum, list_aggregate) and Trino (reduce).

Rationale for this change

DataFusion has array_min and array_max but no array_sum, array_product, or array_avg. These are common operations on array columns that currently require verbose workarounds (UNNEST + aggregate + ARRAY_AGG).

What changes are included in this PR?

New functions:

• array_sum / list_sum — sum of all elements in an array (same return type as element)
• array_product / list_product — product of all elements (rejects Decimal types where raw integer multiplication produces incorrect results due to scale)
• array_avg / list_avg — arithmetic mean, always returns Float64

Bug fixes:

• Added missing list_min alias to ArrayMin (parity with list_max on ArrayMax)
• Extended convert_to_f64_array in vector_math.rs to handle Int8, Int16, UInt8, UInt16, UInt32, UInt64

Implementation:

• array_sum and array_product use the same downcast_primitive! + offset-window pattern as array_min/array_max for zero-copy performance
• array_avg converts elements to Float64 via the shared convert_to_f64_array primitive
• All functions: NULL elements skipped, all-NULL/empty arrays return NULL, List and LargeList supported, FixedSizeList coerced automatically

Dependencies: Builds on #21371 (vector distance + array math functions) for shared vector_math.rs primitives.

Are these changes tested?

Yes — 41 new sqllogictest cases covering:

• Integer, float, unsigned integer inputs
• NULL element handling (skip NULLs, all-NULL → NULL)
• Empty array and NULL input
• LargeList support
• Multi-row queries
• Alias tests (list_sum, list_product, list_avg, list_min)
• Type preservation (arrow_typeof assertions)
• Error cases (string input, Decimal rejection, no arguments)

All existing tests pass (79 unit tests + 2 doctests + sqllogictests).

Are there any user-facing changes?

Yes — three new SQL functions available:

SELECT array_sum([1, 2, 3, 4]);        -- 10
SELECT array_product([2, 3, 4]);       -- 24
SELECT array_avg([1, 2, 3, 4]);        -- 2.5
SELECT list_min([3, 1, 4, 2]);         -- 1 (new alias)