…s at the bottom (#8655)

* change name of template O

* rename

[main] Update dependencies from dotnet/arcade dotnet/sourcelink

This allows us to find `NuGet.config` files that are named `NuGet.Config` or `nuget.config`, all of which are supported by NuGet.  In particular, `nuget.config` is actually the recommended casing for new projects on Linux so this may be increasingly common.

I didn't add an error condition when none of these are found because Arcade does not always need to work with NuGet.config, so this defers the error to when it actually causes a problem.

…0220324.2 (#8677)

[main] Update dependencies from dotnet/sourcelink

* Change code-mirror to use Ubuntu build agent

The idea here is to improve throughput of code-mirror runs by switching from a Windows-based agent to a Linux-based agent. Linux-based agents provision faster. So this should reduce the overall time for a GitHub commit to reach the AzDO repo.

I haven't tested this change since I don't have the necessary permissions or git understanding to fix something that might get screwed up.

Fixes dotnet/core-eng#15402

* Update PowerShell tasks to use PowerShell Core

Co-authored-by: Matt Mitchell <mmitche@microsoft.com>

Co-authored-by: Matt Thalman <mthalman@microsoft.com>

…20323.1 (#8682)

[main] Update dependencies from dotnet/xharness

…322.6 (#8683)

[main] Update dependencies from dotnet/roslyn

* Enable authenticated discovery of dotnet runtime packages

* PR feedback: code cleanup

Co-authored-by: Łukasz Patalas <dev@lukaszpatalas.pl>