Update .NET SDK version and bump Azure.Identity versions

[anamnavi]

PR Summary

This pull request updates dependencies and makes minor adjustments to assembly handling and credential configuration. The most significant changes include upgrading core package versions, adding new package references, and updating assembly initialization logic.

Dependency updates:

• Updated the .NET SDK version in global.json from 8.0.419 to 8.0.421, ensuring builds use the latest patch version.
• Upgraded Azure.Identity package from version 1.14.2 to 1.17.1 in Microsoft.PowerShell.PSResourceGet.csproj for improved authentication support.
• Added System.Buffers package reference (version 4.6.1) to Microsoft.PowerShell.PSResourceGet.csproj to resolve dependency requirements.

Assembly handling improvements:

• Added 'System.Buffers', 'System.ClientModel', 'System.Numerics.Vectors', and 'System.Threading.Tasks.Extensions' to the NetFrameworkLoadFromPath set in ModuleInitAndCleanup.cs to ensure proper assembly loading.
• Included 'System.ClientModel' and 'System.Buffers' in the list of dependencies in doBuild.ps1 for build consistency.

Credential configuration:

• Removed the explicit exclusion of SharedTokenCacheCredential in GetAzAccessToken to potentially allow its use on supported platforms.

PR Context

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[adityapatwardhan]

Check if bumping NuGet works, AFAIK there were issues with it and hence we kept on the 6.9.x version