Enable building ARM64 version of this library

[Alan-Jowett]

This pull request includes significant updates to the build configurations and project files to support multiple architectures (x64 and ARM64). The changes involve modifying the build matrix in GitHub Actions workflows, updating project configuration files, and ensuring conditional compilation settings for different platforms.

GitHub Actions Workflow Updates:

• .github/workflows/build.yml: Added architecture to the build matrix and updated environment variables and commands to support both x64 and ARM64 architectures. Conditional steps were added to ensure certain tests only run on x64. [1] [2] [3] [4] [5] [6]

Project Configuration Updates:

• Directory.Build.props: Added project configurations for Debug, Release, and FuzzerDebug for Win32, x64, and ARM64 platforms. Also included conditional compilation settings based on the platform.

Project File Updates:

• cxplat/cxplat_test/cxplat_test.vcxproj: Removed platform-specific configurations and replaced them with general configurations for Debug, Release, and FuzzerDebug. Simplified the property groups and item definition groups to be platform-agnostic. [1] [2] [3] [4]
• cxplat/src/cxplat_winkernel/cxplat_winkernel.vcxproj: Similar to cxplat_test.vcxproj, removed platform-specific configurations and replaced them with general configurations. Updated item definition groups to support different platforms conditionally. [1] [2] [3] [4] [5] [6] [7]

[nibanks]

Need to update the branch policy now because of the job name changes.