Refine error classifications
Refine error classifications

Started in on reclassifying the #970 errors. Some tests now pass, some pass with EH, others now have more specific issues to track why they fail. Still a bunch more to work through as well. Added two new #970 cases for tests that fail in the lab (with CHK) that I can't repro currently.

Also excluded a few varargs tests, so that for the tests that do run, LLILC does not skip any methods, and normalized all the varargs exclusions to reference dotnet/microsoft#1440.

JosephTremoulet/llilc,russellhadley/llilc,dotnet/llilc,swaroop-sridhar/llilc,adiaaida/llilc,BruceForstall/llilc,russellhadley/llilc,JosephTremoulet/llilc,dotnet/llilc,adiaaida/llilc,kyulee1/llilcjit,kyulee1/llilcjit,JosephTremoulet/llilc,swaroop-sridhar/llilc,adiaaida/llilc,BruceForstall/llilc,kyulee1/llilcjit,swaroop-sridhar/llilc,BruceForstall/llilc,russellhadley/llilc,dotnet/llilc