Fix withKnownIssue not marking test as skipped in nightly toolchains (#1838)

With the introduction of issue severity, the issue payload contains the
flag `isFailure`. If this is true, we were assuming that the issue didn't
meet the severity threshold.

However if an issue is skipped with `withKnownIssue`, `isFailure` would
be false but `isKnown` is true. In this case we still want to record the
issue and have the test be marked as skipped.

Author: plemarquand

src/TestExplorer/TestParsers/SwiftTestingOutputParser.ts

@@ -381,7 +381,7 @@ export class SwiftTestingOutputParser {
             .map(message => MessageRenderer.render(message))
             .join("\n");
 
-        if (payload.issue.isFailure === false) {
+        if (payload.issue.isFailure === false && !payload.issue.isKnown) {
             return;
         }