Add Async variants to IRepository and repository conductor interfaces

[wintondeshong]

As to not leave current projects stranded without a working implementation, please attempt to have our primary use case of SqlServer (rsm-hcd/AndcultureCode.CSharp.Data.SqlServer#5) ready to go before tackling this issue.

Per the issue above, we have an immediate use case with GraphQL data loaders that could leverage having async variants of our various IRepository and repository conductor interfaces.

Methods like...

// IRepository.cs
Task<IResult<IList<T>>> FindAllCommittedAsync(...);
Task<IResult<T>> FindByIdAsync(long id);