ZetaSQL: support aggregations of literal values

[damccorm]

SELECT ARRAY_AGG(1) b FROM UNNEST([1, 2, 3]) a

beam/sdks/java/extensions/sql/zetasql/src/main/java/org/apache/beam/sdk/extensions/sql/zetasql/translation/AggregateScanConverter.java

Line 245 in f2468ba

// Throw an error if aggregate function's input isn't either a ColumnRef or a cast(ColumnRef).

Imported from Jira BEAM-13648. Original Jira may contain additional context.
Reported by: ibzib.