Streaming IAsyncEnumerable<FluxRecord> and IAsyncEnumerable<string>

[adambajguz]

Proposal/Current behavior: Current IQueryApi doesn't allow for streaming raw results, i.e., results of type FluxRecord or string.

Desired behavior:

IAsyncEnumerable<T> QueryAsyncEnumerable<T>(string query, string org = null, CancellationToken cancellationToken = default(CancellationToken));

IAsyncEnumerable<T> QueryAsyncEnumerable<T>(Query query, string org = null, CancellationToken cancellationToken = default(CancellationToken));

When T is string or FluxRecord don't map the result to POCO.

Alternatives considered: Add new methods that return IAsyncEnumerable<string> and IAsyncEnumerable<FluxRecord>.

Use case: Current methods with delegates are not flexible enought (e.g. callbacks cannot use async code). Also its not always desired to map to POCO from performance reasons.