Add CancellationToken optional parameter to all Async methods

[mcenzato]

I saw that a lot of Dapper async methods (eg. QueryAsync) miss the CancellationToken parameter.

[Rendojack]

You can workaround this by passing CommandDefinition with assigned CancellationToken in most of the simple queries, except more complicates ones, like with multi-mapping.

[digibum]

A friendly reminder for this. Especially for multi-mapping and a simpler implementation without the need for CommandDefinition. Just add an optional parameter to the basic Query methods. Thank you!