[Response Ops][Actions] Using fake request to create scoped client for ConnectorTokenClient unsecured actions usage. (#223447)

## Summary

Addresses a bug with the `ConnectorTokenClient` when using the
`UnsecuredActionClient` to execute actions directly (vs enqueuing a task
for execution). We previous pass in an internal saved objects repository
(that doesn't require a user request) to the `ConnectorTokenClient` when
using the `UnsecuredActionsClient` but this does not create the
`connector_token` saved object correctly so the next time it's read, we
get a `Failed to decrypt attribute` error.

This only occurs when using the `sendAttachmentEmail` with the MS
Exchange connector function added in this PR:
https://github.com/elastic/kibana/pull/219164. It does not affect the
other email service methods.

## To Verify

1. Ask me for MS Exchange credentials
2. Add this to your Kibana config:

```
xpack.actions.preconfigured:
  test-exchange-email:
    name: preconfigured-exchange-email
    actionTypeId: .email
    config:
      service: exchange_server
      clientId: <clientId>
      tenantId: <tenantId>
      from: <from>
    secrets:
      clientSecret: <secret>
notifications.connectors.default.email: test-exchange-email
```
3. Make this change to the code so Kibana sends 2 emails when it starts
up:

```
--- a/x-pack/platform/plugins/shared/notifications/server/plugin.ts
+++ b/x-pack/platform/plugins/shared/notifications/server/plugin.ts
@@ -40,6 +40,27 @@ export class NotificationsPlugin
   public start(_core: CoreStart, plugins: NotificationsServerStartDependencies) {
     const emailStartContract = this.emailServiceProvider.start(plugins);

+    const emailService = emailStartContract.getEmailService();
+    emailService
+      .sendAttachmentEmail({
+        to: ['<email>'],
+        subject: 'yo',
+        message: 'i am here',
+        attachments: [],
+        spaceId: 'default',
+      })
+      .then(() => {
+        new Promise((resolve) => setTimeout(resolve, 5000)).then(() => {
+          emailService.sendAttachmentEmail({
+            to: ['<email>'],
+            subject: 'yo',
+            message: 'i am here again',
+            attachments: [],
+            spaceId: 'default',
+          });
+        });
+      });
+
     return {
```

4. Verify there are no decryption errors for the `connector_token` SO
logged and that the emails are sent successfully.

Co-authored-by: Elastic Machine <elasticmachine@users.noreply.github.com>

x-pack/platform/plugins/shared/actions/server/plugin.ts

@@ -558,7 +558,7 @@ export class ActionsPlugin
         getInternalSavedObjectsRepositoryWithoutAccessToActions,
         core.elasticsearch,
         encryptedSavedObjectsClient,
-        () => core.savedObjects.createInternalRepository(includedHiddenTypes)
+        () => this.getUnsecuredSavedObjectsClientWithFakeRequest(core.savedObjects)
       ),
       encryptedSavedObjectsClient,
       actionTypeRegistry: actionTypeRegistry!,
@@ -635,6 +635,24 @@ export class ActionsPlugin
       includedHiddenTypes,
     });
 
+  // replace when https://github.com/elastic/kibana/issues/209413 is resolved
+  private getUnsecuredSavedObjectsClientWithFakeRequest = (
+    savedObjects: CoreStart['savedObjects']
+  ) => {
+    const fakeRequest = {
+      headers: {},
+      getBasePath: () => '',
+      path: '/',
+      route: { settings: {} },
+      url: { href: {} },
+      raw: { req: { url: '/' } },
+    } as unknown as KibanaRequest;
+    return savedObjects.getScopedClient(fakeRequest, {
+      excludedExtensions: [SECURITY_EXTENSION_ID],
+      includedHiddenTypes,
+    });
+  };
+
   private instantiateAuthorization = (request: KibanaRequest) => {
     return new ActionsAuthorization({
       request,
@@ -665,7 +683,7 @@ export class ActionsPlugin
     getSavedObjectRepository: () => ISavedObjectsRepository,
     elasticsearch: ElasticsearchServiceStart,
     encryptedSavedObjectsClient: EncryptedSavedObjectsClient,
-    unsecuredSavedObjectsRepository: () => ISavedObjectsRepository
+    unsecuredSavedObjectsRepository: () => SavedObjectsClientContract
   ): () => UnsecuredServices {
     return () => {
       return {