feat(6222): remove @ and project from OIDC client ID (#8178)

# Which Problems Are Solved

The client ID for OIDC applications has an `@` in it, which is not
allowed in some 3rd-party systems (such as AWS).

# How the Problems Are Solved

Per @fforootd and @hifabienne in #6222, remove the project suffix and
the `@` from the client ID and just use the generated ID.

# Additional Changes

N/A

# Additional Context

- Closes #6222

---------

Co-authored-by: Stefan Benz <46600784+stebenz@users.noreply.github.com>
Co-authored-by: Livio Spring <livio.a@gmail.com>

internal/query/testdata/oidc_client_no_settings.json

@@ -2,7 +2,7 @@
   "instance_id": "239520764275982338",
   "app_id": "239520764276441090",
   "state": 1,
-  "client_id": "239520764779364354@zitadel",
+  "client_id": "239520764779364354",
   "client_secret": null,
   "redirect_uris": [
     "http://test2-qucuh5.localhost:9000/ui/console/auth/callback",