meta: Add visibility to codeowners for performance utils (#24267)

This also moves some tests into the `tests/js/spec/utils/performance/` folder.

.github/CODEOWNERS

@@ -129,6 +129,8 @@ build-utils/        @getsentry/owners-js-build
 /tests/js/spec/views/performance/                               @getsentry/visibility
 /src/sentry/static/sentry/app/utils/discover/                   @getsentry/visibility
 /tests/js/spec/utils/discover/                                  @getsentry/visibility
+/src/sentry/static/sentry/app/utils/performance/                @getsentry/visibility
+/tests/js/spec/utils/performance/                               @getsentry/visibility
 /src/sentry/static/sentry/app/views/dashboards/                 @getsentry/visibility
 /tests/js/spec/views/dashboards/                                @getsentry/visibility
 /src/sentry/static/sentry/app/views/dashboardsV2/               @getsentry/visibility