Move task environment drivers to Framework.

[AR-May]

Context

Task environment drivers must be moved to Framework projects so they can be invoked from tasks. This is a prerequisite for the RAR task enlightening and for fixing #13374.

Changes Made

• Moved the task environment drivers to the Framework project
• Moved environment-related function from CommunicationsUtilities to the Framework project
• Split in half DebugUtils and moved relevant part to the Framework project. There is quite weird code path in CommunicationsUtilities.GetEnvironmentVariablesWindows where it ensures the DebugUtils static constructor is called because it sets the environment variables that we would like then to propagate to other msbuild processes.

Testing

• Unit tests
• Exp insertion

[Copilot]

Pull request overview

This PR refactors MSBuild’s debugging and environment-variable handling by moving the relevant helper logic out of Shared/Internal and into Microsoft.Build.Framework-scoped helpers, then updating engine/taskhost/unit-test call sites accordingly.

Changes:

• Introduces FrameworkDebugUtils and FrameworkCommunicationsUtilities in src/Framework and updates call sites to use them.
• Removes the environment-variable caching/restore helpers from src/Shared/CommunicationsUtilities.cs and rehomes that logic in the Framework layer.
• Moves task environment drivers to the Microsoft.Build.Framework namespace and updates the engine/tests to use the relocated types.

Reviewed changes

Copilot reviewed 21 out of 21 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/Shared/UnitTests/CommunicationUtilities_Tests.cs	Updates env-var tests to use FrameworkCommunicationsUtilities.
src/Shared/Debugging/PrintLineDebugger.cs	Switches process-info prefix source to FrameworkDebugUtils.
src/Shared/Debugging/DebugUtils.cs	Removes static init responsibilities and delegates debug-path usage to FrameworkDebugUtils.
src/Shared/CommunicationsUtilities.cs	Removes env-var caching/restore logic and updates trace dump path to use FrameworkDebugUtils.
src/MSBuild/XMake.cs	Uses FrameworkDebugUtils for debug-path and TaskHost-node detection.
src/MSBuild/OutOfProcTaskHostNode.cs	Switches env snapshot/restore to FrameworkCommunicationsUtilities.
src/Framework/MultiThreadedTaskEnvironmentDriver.cs	Moves driver into Microsoft.Build.Framework and uses framework env-var comparer.
src/Framework/MultiProcessTaskEnvironmentDriver.cs	Moves driver into Microsoft.Build.Framework and uses FrameworkCommunicationsUtilities/NativeMethods.
src/Framework/DebugUtils.cs	Adds FrameworkDebugUtils (debug path + process diagnostics).
src/Framework/CommunicationsUtilities.cs	Adds FrameworkCommunicationsUtilities (env-var caching + set/restore).
src/Build/Utilities/Utilities.cs	Switches environment properties sourcing to FrameworkCommunicationsUtilities.
src/Build/Microsoft.Build.csproj	Stops compiling task environment drivers from the Build project (now in Framework).
src/Build/BackEnd/Node/OutOfProcServerNode.cs	Uses FrameworkCommunicationsUtilities.SetEnvironment.
src/Build/BackEnd/Node/OutOfProcNode.cs	Uses FrameworkCommunicationsUtilities for env snapshot/restore.
src/Build/BackEnd/Node/InProcNode.cs	Uses FrameworkCommunicationsUtilities for env snapshot/restore.
src/Build/BackEnd/Components/Scheduler/Scheduler.cs	Uses FrameworkDebugUtils.DebugPath.
src/Build/BackEnd/Components/BuildRequestEngine/BuildRequestEngine.cs	Uses FrameworkDebugUtils.DebugPath.
src/Build/BackEnd/BuildManager/BuildParameters.cs	Uses FrameworkCommunicationsUtilities for env snapshots.
src/Build/BackEnd/BuildManager/BuildManager.cs	Uses FrameworkDebugUtils for debug gating and process info strings.
src/Build.UnitTests/BackEnd/TaskExecutionHost_Tests.cs	Updates tests to call FrameworkDebugUtils.SetDebugPath.
src/Build.UnitTests/BackEnd/DebugUtils_tests.cs	Updates tests to validate FrameworkDebugUtils behavior.