Fix detection of torn SDK

[jjonescz]

If I understand correctly, the SDK is torn in case we have an old msbuild and new SDK. So e.g., if $(_MSBuildVersionMajorMinor) is 17.10 and $(_BundledMSBuildVersionMajorMinor) is 17.11 then $(_IsDisjointMSBuildVersion) should be true.

Part of https://github.com/dotnet/sdk/issues/41791.