Fix 'previous failures' in watch mode always incrementing

The counters used absolute paths for the test files, but the clearing logic used relative paths. Count using relative paths instead.

The number of previous failures is not observable to the test harness, so this does not come with test coverage.

Fixes #3295.

lib/watcher.js

@@ -106,7 +106,8 @@ async function * plan({api, filter, globs, projectDir, providers, stdin, abortSi
 				case 'uncaught-exception':
 				case 'unhandled-rejection':
 				case 'worker-failed': {
-					failureCounts.set(evt.testFile, 1 + (failureCounts.get(evt.testFile) ?? 0));
+					const path = nodePath.relative(projectDir, evt.testFile);
+					failureCounts.set(path, 1 + (failureCounts.get(path) ?? 0));
 					break;
 				}