Change version check from != to < to allow loading newer assembly versions when older versions are requested.

[huulinhnguyen-dev]

Fixes #
Change version check from != to < to allow loading newer assembly versions when older versions are requested. #12370

Context

MSBuildLoadContext was using exact version matching (!=) when loading assemblies, preventing version roll-forward. This caused tasks to fail when requesting an older assembly version even though a newer compatible version was available.

Changes Made

• Changed version comparison in MSBuildLoadContext.cs from != to < (line 86)
• Added unit test MSBuildLoadContext_AcceptsNewerAssemblyVersions in TaskBuilder_Tests.cs
• Added test task ValidateAssemblyVersionRollForward in AssemblyLoadContextTestTasks.cs

Testing

• Added unit test that verifies assembly version roll-forward behavior
• Test requests System.Collections.Immutable v1.0.0.0 and verifies newer version loads successfully
• Test only runs on platforms with FEATURE_ASSEMBLYLOADCONTEXT (.NET Core/.NET 5+)

Notes

This change allows MSBuildLoadContext to accept any assembly version >= requested version, matching standard .NET assembly loading behavior.