[devtools] Throw adding 2 internal authenticators

Have devtools throw an error when a client attempts to add an internal
authenticator when there's one already present in the environment. This
is not supported and causes all sorts of issues.

This requires fixing a WPT that did not clean the virtual
authenticator. The WPT passing and not crashing Chrome previously was
luck.

Fixed: 40234612
Change-Id: I25d6e6c3387d0180234c21af157bc0b6ef15f566
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6047769
Reviewed-by: Alex Rudenko <[email protected]>
Auto-Submit: Nina Satragno <[email protected]>
Commit-Queue: Alex Rudenko <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1388668}

permissions-policy/resources/permissions-policy-payment-extension.html

@@ -15,7 +15,7 @@
 
 window.onload = async function() {
   test_driver.set_test_context(parent);
-  await window.test_driver.add_virtual_authenticator(authenticatorArgs);
+  const authenticator = await window.test_driver.add_virtual_authenticator(authenticatorArgs);
   let enabled = true;
   let name = `OK`;
   try {
@@ -56,6 +56,7 @@
     enabled = false;
     name = e.name;
   }
+  await window.test_driver.remove_virtual_authenticator(authenticator);
   parent.postMessage({ type: 'availability-result', enabled, name }, '*');
 }
 </script>