migrate-mstest-v1v2-to-v3

Migrate MSTest v1 or v2 test project to MSTest v3. Use when user says "upgrade MSTest", "update test framework", "modernize tests", or has build errors after updating MSTest packages from 1.x/2.x. USE FOR: upgrading from MSTest v1 assembly references (Microsoft.VisualStudio.QualityTools.UnitTestFramework) or MSTest v2 NuGet (MSTest.TestFramework 1.x–2.x) to MSTest v3, fixing assertion overload errors (AreEqual/AreNotEqual), updating DataRow constructors, replacing .testsettings with .runsettings, timeout behavior changes, target framework compatibility (net5.0 unsupported — use net6.0+; .NET Fx < 4.6.2 unsupported), adopting MSTest.Sdk, parallel execution. First step toward MSTest v4 — after this, use migrate-mstest-v3-to-v4. DO NOT USE FOR: migrating to MSTest v4 (use migrate-mstest-v3-to-v4), migrating between frameworks (MSTest to xUnit/NUnit), or general .NET upgrades unrelated to MSTest.