* Update pre-release label and add triggers

* Update Versions.props

[main] Update dependencies from dotnet/arcade


 - Update image used; it seems the GA 6.0.100 .NET Core SDK wants VS 2022 for WPF's purposes.

 - Temporarily change to Int pools for verification

 - Revert "Temporarily change to Int pools for verification"

This reverts commit 266cd39779e3f336854453b37fffae8f9be5f037.

 - Change platform Toolset to 143

 - Merge branch 'darc-main-83d344b6-2da4-4cb4-bc09-b0c292dfa886' of https://github.com/dotnet/wpf into darc-main-83d344b6-2da4-4cb4-bc09-b0c292dfa886

 - Update VCRuntime  VC version

 - Temporarily change pool to internal

 - Change toolsversion to 17

 - temporarily remove atl lib dependency

Temporarily disable PR builds in main to prevent builds for all open PRs from running when changing the default branch

Enables post build signing. This repo will discontinue signing in-build and instead the entire product will sign all at once in the staging pipelines.

Reduces build time. SDL is now right nightly + on each build candidate. No need to keep running on a per-build basis.

* Update dependencies from https://github.com/dotnet/winforms build 20191114.3 (#2192)

- Microsoft.Private.Winforms - 4.8.1-rtm.19564.3

* Update dependencies from https://github.com/dotnet/winforms build 20191114.4 (#2194)

- Microsoft.Private.Winforms - 4.8.1-rtm.19564.4

* add internal/release/3.* to PR trigger list

* Update Versions.props for release/3.1
* Add support for building release/3.1
* Remove ProductVersion
* Add release/3.1 for PR builds

Re-enable release/3.0 build trigger

* Update branding to RC1
* Re-enable release/3.0 branch in triggers
* Update dependencies

Fix typo (missing newline) in yml file

* Re-enable SDL validation build step.

* Removing vestigial comment

* Update for YAML stages
* Temporarily disable SDL validation until https://github.com/dotnet/arcade/issues/3565 gets resolved.

* Change _TestHelixAgentPool from 19H1 to RS5

* - Further restric the Agent Pools to Windows.10.Amd64.CleintRS5 - this is the only one that seems immune to timeouts
- Limit Helix test runs to the open build pipline. Do not repeat the same tests in the internal pipeline.

* Setting build timeout to 120 mins

Add PresentationFramework, PresentationCore, WindowsBase, DirectWriteForwarder sources, along with sources for allied assemblies