[GrahamTheCoder]

Fixes #932
Fixes #1302
Fixes #895

All three already convert correctly on master since #1305. This PR only adds tests to pin that.

#932: Group By keys named differently from their members

• New conversion test Issue932_GroupByKeysNamedDifferentlyFromTheirMembersAsync, using the issue's query. The keys keep their names (new { Agent_First_Name = agent.First_Name, ... }) and the output compiles.
• New self-verifying test TestGroupByKeysNamedDifferentlyFromTheirMembers. It runs a joined Group By with renamed keys in both VB and C# and compares the results.

#1302: generic method inference with a contravariant base-type comparer

VB infers an extension method's type arguments from the receiver first, then converts the other arguments; C# infers from all arguments together, so would infer BaseValue here. Where an argument only fits its generic parameter via a variance conversion, the converter now states the type arguments VB inferred: values.Distinct<DerivedValue>(EqualityComparer<BaseValue>.Default).

• Conversion test Issue1302_GenericMethodInferenceWithBaseTypeComparerAsync (the issue's code) and self-verifying test TestGenericMethodInferenceWithBaseTypeComparer.
• GenericMethodWithInterfaceConversionKeepsTypeArgumentsInferredAsync checks an ordinary interface conversion doesn't add type arguments.
• The first version of this PR expected a cast that only some environments produced, which is why CI failed.

#895: Where after Group By

Already covered:

• by the conversion test Issue895_LinqWhereAfterGroupAsync, which now expects where Group.Count() > 1 select new { x = Group.Key, Group };
• by the self-verifying test TestWhereAfterGroup, which runs the issue's query in VB and C#.