Cleanup System.Linq.AsyncEnumerable

[adamsitnik]

Each project that uses any kind of custom IAsyncEnumerable extensions that are going to be available in 10, should switch to the new .NET 10 package once it gets published on Tuesday.

Samples:

extensions/test/Libraries/Microsoft.Extensions.DataIngestion.Tests/Utils/IAsyncEnumerableExtensions.cs

Line 13 in b839e41

internal static async IAsyncEnumerable<T> ToAsyncEnumerable<T>(this IEnumerable<T> source)

extensions/test/Libraries/Microsoft.Extensions.AI.Tests/ChatCompletion/ReducingChatClientTests.cs

Line 166 in b839e41

private static async IAsyncEnumerable<T> ToAsyncEnumerable<T>(IEnumerable<T> items)

extensions/src/Libraries/Microsoft.Extensions.DataIngestion/Utils/Batching.cs

Line 75 in ca4fc52

private static IAsyncEnumerable<TSource[]> Chunk<TSource>(this IAsyncEnumerable<TSource> source, int count)

cc @stephentoub