SQL avg(field) function is broken with multiple group by

Avg function doesn't work if you are grouping by multiple group by.
The issue is reproducible through an ad hoc integration test in:
org.alfresco.solr.query.stream.DistributedGroupBySqlIT
e.g.

sql = "select mf_freetext_underscore as underscoreField, count(mf_freetext_underscore) as numUnderscore, exif_manufacturer, finance_title" +
                    "cm_created,  " +
                    "count(*) as ExposureCount,  " +
                    "sum(exif_exposureTime) as TotalExposure,  " +
                    "avg(exif_exposureTime) as AvgExposure,  " +
                    "min(exif_exposureTime) as MinExposure,  " +
                    "max(exif_exposureTime) as MaxExposure  " +
                "from alfresco  " +
                "where  " +
                    "exif_exposureTime > 0 and  " +
                    "cm_content='world' and  " +
                    "cm_created BETWEEN '2000-01-01T01:01:01Z' AND '2010-02-14T23:59:59Z'" +
                "group by mf_freetext_underscore, exif_manufacturer,finance_title";

The reason is that Calcite parses the avg function as avg when there's just one group by.
When there are multiple group by it is parsed as SUM(field)/COUNT(field).

This is noticeable here: org.alfresco.solr.sql.SolrTable.SolrQueryable#query

Taking a look to List<Pair<String, String>> metricPairs input for both the scenarios, the difference is clear (with the multiple group by you see the DIVISION in the String operations input parameter).

org.alfresco.solr.sql.SolrTable.SolrQueryable#query is kinda the Alfresco custom code entry point, so I suspect the bug may be Calcite side.
I was not able to find an elegant solution with a quick fix, addressing it may require some work (unless we opt for a brute workaround).

Acceptance criteria :

• avg function works when you group by multiple fields
• few new integration tests are added for that specific use case in org.alfresco.solr.query.stream.DistributedGroupBySqlIT
• avg(CAST(cm_sizeCurrent AS DOUBLE)) as AvgSize returns the double average even if cm_sizeCurrent was originally BIGINT