Query: Adds LINQ support for Multi-key Group By translation

[leminh98]

Pull Request Template

Description

This PR features the new syntax for multi-key group by queries, allowing for grouping of multiple properties.

Full syntax:

// Function Signature
public static System.Collections.Generic.IEnumerable<System.Linq.IGrouping<TKey,TElement>> GroupBy<TSource,TKey,TElement> (this System.Collections.Generic.IEnumerable<TSource> source, Func<TSource,TKey> keySelector, Func<TSource,TElement> elementSelector);

// Usage
Enumerables.GroupBy( groupByKeys => keySelectiorLambda, (keys, values) => valueSelectorLambda);

Example

• Grouping by single keys and projecting single value

Enumerable.GroupBy( /*keySelector*/ k => k.Id,  /*valueSelector*/ (key, values) => values.Count());

• Grouping by single keys and projecting multiple values

Enumerable.GroupBy( 
              /*keySelector*/ k => k.Id, 
              /*valueSelector*/ (key, values) => new
               {
                   idField = key.key1,
                   count = values.Count(),
               });

• Grouping by multiple keys and projecting single value

Enumerable.GroupBy( 
              /*keySelector*/  k => new
                 {
                     key1 = k.Id,
                     key2 = k.Int
                 } , 
              /*valueSelector*/ (key, values) => values.Count());

• Grouping by multiple keys and projecting multiple values

Enumerable.GroupBy(
/*keySelector*/
              k => new
                  {
                      key1 = k.Id,
                      key2 = k.Int
                  } , 
/*valueSelector*/
                (key, values) => new
                {
                    idField = key.key1,
                    count = values.Count(),
                })

Type of change

Please delete options that are not relevant.

• [] Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• [] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [] This change requires a documentation update

Closing issues

closes ##1202