CsvWriter.WriteRecordsAsync does not dispose e.g. EF Core AsyncEnumerators

[CaringDev]

The CsvWriter.WriteRecordsAsync overload for IAsyncEnumerable<T> creates an IAsyncEnumerator but does not dispose implementations not implementing IDisposable. When using EF Core with streaming results this leads to concurrent queries on the same DbContext. As this is not allowed e.g. for Postgres a Npgsql.NpgsqlOperationInProgressException is thrown on subsequent operations.
As IAsyncEnumerator implements IAsyncDisposable we should unconditionally await DisposeAsync.

[vchirikov]

Oh, didn't see the issue, my PR for this is #2297