fix(TypeHandler): use the custom type handler when packing a list parameter

[tlecomte]

Fixes #2067

The code for SqlMapper.PackListParameters was not using the custom type handler. This caused an error like No mapping exists from object type xxxxx to a known managed provider native type. when passing a collection parameter to a query, when the type of the collection items is not natively supported by the SQL client, and when a custom TypeHandler is registered for it.

Here this is fixed by using the same logic that is already in DynamicParameters.AddParameter.

A unit test is added to cover the scenario.

[tlecomte]

Dear @mgravell, please see here a PR to fix an issue with list parameters and custom type handlers. Thank you very much for considering this!