[EngSys] Trim additional polyfill packages

[jsquire]

Summary

To ensure consistency across targets, polyfill packages are available on NuGet for these system features supported by netstandard2.0. On runtimes where the features are missing, the polyfill packages provide them. On runtimes where the features are natively available, the polyfill packages do nothing. This was helpful in the early days of .NET Core, where the runtime feature set was undergoing many changes. Starting with .NET 6, some of the features that the Azure SDK packages rely on are available natively in the runtime.

An initial wave of trimming for built-in features exists was added to Directory.Build.Common.targets and has been undergoing compatibility testing during our CI and nightly test runs.

We should be able to add the following packages as additional trims:

• Microsoft.Bcl.AsyncInterfaces
• System.Threading.Tasks.Extensions

Scope of work

• Add the additional packages as targets for trimming
• Run the Core and ResourceManager CI and nightly test pipelines to validate
• Monitor CI and nightly failures across the Azure SDK for .NET packages for a week to find any regressions

Success criteria

CI and nightly test runs continue to pass consistently and reliably