Full ARM64 support

ARM64 VMs have been available on Azure for a while now, and we have a corresponding 1ES Hosted Pool which provides ARM64 VM access to CI runs that want to use ARM64. But what's lacking at this moment are the images used for the CI jobs, they're bare bones, lacking basic tools we need such as PowerShell, etc.

This is a request for eventually having full ARM64 support out of the box that would allow all our Azure SDK and related repositories be able to just select the image, do minor tweaks needed based on what's needed for the specific CI job, and just work.

This is not an urgent request, but something we'd want to work towards in the future given how ARM is becoming more and more prevalent and how it would be good for our CI to test scenarios customers can currently use our products in.

An example of attempting to use ARM64 in microsoft/mcp using our hosted pool: https://github.com/microsoft/mcp/pull/656

Start by reviewing the Azure 1ES Hosted Pool and the ARM64 images used by CI runs. Compare the bare-bones images with the tools required by Azure SDK and related repositories, including PowerShell, and use microsoft/mcp#656 as an example. Done means an ARM64 image can be selected with only minor job-specific tweaks and supports the needed CI scenarios.

Written by the indexing model from the issue text.