New: Adding Facepunch.Tests assembly for unit testing Facepunch libs, with ListExtension tests Motivation: when working on core libraries we gotta have confidence that we won't bork something somewhere by changing core algos&utils. With this test assembly, we have a common place to document behavior of Facepunch lib before we go modify it. Added 64 test cases for ListExtension changes (I couldn't reliably confirm in 3p multiplayer session). Test assembly configured in lean fashion. Tests: built all targets in editor. Ran all existing tests, including new ones being submitted. Observed ~10 failures in NavMesh and TextMeshPro, but new tests pass.