Add a test for PermissionsPolicyViolationReportBody

[Elchi3]

I couldn't find good docs on MDN about this :(
https://github.com/w3c/webappsec-permissions-policy/blob/main/reporting.md has some good info, though.

I reckon we need some custom test like below plus a way to actually trigger a permission policy violation.

  PermissionsPolicyViolationReportBody:
    __base: |-
      // Note: the Content-Security-Policy header is already configured on this website
      if (!('ReportingObserver' in self)) {
        return {result: false, message: 'ReportingObserver is not defined'};
      }

      // Create the observer
      var observer = new ReportingObserver(
        function(reports, observer) {
          var instance = reports.length && reports[0].body;
          callback(instance);
          observer.disconnect();
        },
        {
          types: ["permissions-policy-violation"],
          buffered: true,
        }
      );

      // Start observing
      observer.observe();
    toJSON: |-
      function callback(instance) {
        try {
          success(!!instance && 'toJSON' in instance);
        } catch(e) {
          fail(e);
        }
      }
      return 'callback';

PermissionsPolicyViolationReportBody ships in Chrome 120 and wasn't detected by our collector, see mdn/browser-compat-data#21148 (comment)