Query: Adds asynchronous enumeration

[seesharprun]

Description

I've always wanted to use the new await foreach and this PR is an attempt to implement the IAsyncEnumerable<> interface in two places:

• As an interface for FeedIterator<> to give consumers another option for querying entities

  QueryDefinition query = new QueryDefinition(
      query: "SELECT * FROM items i WHERE i.pk = @pk ORDER BY i.cost"
  ).WithParameter("@pk", "<partition-key>");    
  
  FeedIterator<Item> feedIterator = this.Container.GetItemQueryIterator<Item>(query);
  
  IAsyncEnumerable<FeedResponse<Item>> pages = feedIterator.AsAyncEnumerable();

• As an extension method AsAsyncEnumerable() for CosmosLinqQuery<> queries

  IAsyncEnumerable<FeedResponse<Item>> pages = this.Container.GetItemLinqQueryable<Item>()
      .Where(i => i.pk == "<partition-key>")
      .OrderBy(i => i.cost)
      .AsAsyncEnumerable();

This is a pretty major lift, so I anticipate some major changes and opinionated reviews. This is based on @onionhammer work in #4355. I've implemented a few of the items of feedback from the engineering team:

• First, I made sure you can get an asynchronous iterator from either the "LINQ" or "NoSQL query" options for a Container instance.

• Second, I added unit and emulator tests for both options. I was unable to mock the CosmosLinqQuery<> type because it was sealed, so I would appreciate guidance on unit testing for that scenario.

• Finally, I returned an IAsyncEnumerable<FeedResponse<>>. This balances between the convenience of await foreach and the depth of reading response metadata/headers. Here's an example query:

  double requestCharge = 0.0;
  List<Item> results = new();
  await foreach(var page in pages)
  {
      requestCharge += page.RequestCharge;
      foreach (var item in page)
      {
          items.Add(item);
      }
  }

I also tried to be as verbose as possible with the XML comments so they can generate into the documentation with examples.

Type of change

• New feature (non-breaking change which adds functionality)
• This change requires a documentation update

Closing issues

• Closes Add support for IAsyncEnumerable<T> #903

[seesharprun]

It looks like these two tests are failing in the preview run:

• EnumIsPreservedAsINTest
• PreviewContractChanges

[seesharprun]

I'm not sure why the preview tests are failing