Add CancellationToken support for MultiMap Queries.

Add overload methods for MultiMap queries to pass CancellationToken to CommandDefinition.

From this:

public static IEnumerable<TReturn> Query<TReturn>(this IDbConnection cnn, string sql, Type[] types, Func<object[], TReturn> map, object? param = null, IDbTransaction? transaction = null, bool buffered = true, string splitOn = "Id", int? commandTimeout = null, CommandType? commandType = null)
{
    var command = new CommandDefinition(sql, param, transaction, commandTimeout, commandType, buffered ? CommandFlags.Buffered : CommandFlags.None);
    var results = MultiMapImpl(cnn, command, types, map, splitOn, null, null, true);
    return buffered ? results.ToList() : results;
}

To this:

public static IEnumerable<TReturn> Query<TReturn>(this IDbConnection cnn, string sql, Type[] types, Func<object[], TReturn> map, object? param = null, IDbTransaction? transaction = null, bool buffered = true, string splitOn = "Id", int? commandTimeout = null, CommandType? commandType = null, CancellationToken ct = CancellationToken.None)
{
    var command = new CommandDefinition(sql, param, transaction, commandTimeout, commandType, buffered ? CommandFlags.Buffered : CommandFlags.None, ct);
    var results = MultiMapImpl(cnn, command, types, map, splitOn, null, null, true);
    return buffered ? results.ToList() : results;
}

EDIT:

Another aproach would be to give access to some private methods like:
MultiMapImpl
where we could manually build CommandDefinition with CancellationToken assigned to it.

Start with the MultiMap Query overload shown in the issue and trace how it calls MultiMapImpl and constructs CommandDefinition. Identify the related MultiMap overloads that need the same CancellationToken support; done means callers can pass a token through to CommandDefinition for these queries.