Add missing exception messages

[ajcvickers]

• efcore/src/EFCore.Relational/Query/StructuralTypeProjectionExpression.cs

  Line 310 in ecfc1ce

  throw new InvalidOperationException(); // TODO: Message

• efcore/src/EFCore.Relational/Query/StructuralTypeProjectionExpression.cs

  Line 333 in ecfc1ce

  throw new InvalidOperationException(); // TODO: Message

• efcore/src/EFCore.Relational/Query/RelationalSqlTranslatingExpressionVisitor.cs

  Line 1893 in ecfc1ce

  throw new InvalidOperationException(); // TODO: Message

• efcore/src/EFCore.SqlServer/Query/Internal/SqlServerQueryableMethodTranslatingExpressionVisitor.cs

  Line 612 in ecfc1ce

  // TODO: Message

• efcore/src/EFCore/Query/IEntityMaterializerSource.cs

  Line 66 in ecfc1ce

  : throw new InvalidOperationException(); // TODO