Use xunit trait for filter away tests which can only run live

1. So we wiill use xunit runner 2.0 which has a new msbuild runner task with built-in support for filtering by trait
2. I removed the workaround of doing skipping on test code 
3. I cleaned up several test targets with assumption of using mstest.exe, which is no longer valid after we migrated to xunit 
note: i updated the verbose to be 'false' so that the CI build logger displays major steps much clearer; rather get buried. If there is failure, you still see the stack trace in the log file. But let me know if you still like see verbosity by default for a helpful reason.