API that allows to remove all assigned handlers from the HTTP client

[rainsxng]

Background and motivation

.NET provides the ConfigureHttpClientDefaults method that allows you to configure the default behavior of the HttpClient. With the help of this method you can register the StandardResiliencePipeline as part of the default configuration of the HttpClient:

services.ConfigureHttpClientDefaults(builder => builder.AddStandardResilienceHandler());

This is convenient, since you don't need to configure the resilience pipeline for each HttpClient. But with the API we currently provide users face a few issues/challenges when they need to change the default configuration. This change focuses on the following issue:

Removing the existing default resilience pipeline and adding a custom one

For example, a user registers the StandardResilienceHandler as default configuration, but at the same time he/she wants to use the StandardHedgingHandler for a particular named HttpClient:

services.ConfigureHttpClientDefaults(builder => builder.AddStandardResilienceHandler());

// For a named HttpClient "custom" we want to remove the StandardResilienceHandler and add instead the StandardHedgingHandler.
services.AddHttpClient("custom")./*Remove StandardResilienceHandler*/.AddStandardHedgingHandler();

API description

This API provides functionality to remove all assigned handlers from the HttpClient.

API Usage

services.ConfigureHttpClientDefaults(builder => builder.AddStandardResilienceHandler());
// For a named HttpClient "custom" we want to remove the StandardResilienceHandler and add instead the StandardHedgingHandler.
services.AddHttpClient("custom")
    .RemoveAllResilienceHandlers()
    .AddStandardHedgingHandler();

This PR partially resolves #5695

Microsoft Reviewers: Open in CodeFlow

[iliar-turdushev]

This will remove all http message handler types, but we need to remove only handlers of type ResilienceHandler.

[rainsxng]

Updated

[dotnet-comment-bot]

🎉 Good job! The coverage increased 🎉
Update MinCodeCoverage in the project files.

Project	Expected	Actual
Microsoft.Extensions.AI	88	89
Microsoft.Extensions.AI.OpenAI	77	78

Full code coverage report: https://dev.azure.com/dnceng-public/public/_build/results?buildId=923055&view=codecoverage-tab