Linux test fixes

Because sys.newLine asks node for the OS's newline character(s) we have different baseline results on Windows vs *nix for certain tests. In particular, our sourcemap baselines were all failing on Linux. This fixes that by defaulting to \r\n for all newlines and allowing tests to opt into using \n using @ newline metadata in tests. There were a handful of other tests that had file casing issues that caused them to fail on Linux, none of which looked to be intentionally testing casing issues.
This change looks like it might not be relevant this this PR.