revert: "feat(IDP): use single callback endpoint"

This reverts commit e126ccc9aa.

# Which Problems Are Solved

#8295 introduced the possibility to handle idps on a single callback,
but broke current setups.

# How the Problems Are Solved

- Revert the change until a proper solution is found. Revert is needed
as docs were also changed.

# Additional Changes

None.

# Additional Context

- relates to #8295

docs/docs/guides/integrate/identity-providers/azure-ad-saml.mdx

@@ -72,7 +72,7 @@ Now we configure the identity provider on ZITADEL.
 
 After you created the SAML provider in ZITADEL, you can copy the URLs you need to configure in your Entra ID application.
 
-![Azure SAML App URLs](/img/guides/zitadel_saml_provider_urls.png)
+![Azure SAML App URLs](/img/guides/zitadel_azure_saml_provider_urls.png)
 
 1. Go to Microsoft Entra > Manage > Single sign-on
 2. Edit the "Basic SAML Configuration"

docs/docs/guides/integrate/identity-providers/linkedin_oauth.mdx

@@ -23,8 +23,8 @@ import TestSetup from './_test_setup.mdx';
 2. Add your App Name, your Company Page and a Logo
 3. Add "Sign In with LinkedIn using OpenID Connect" by clicking "Request access"
 4. Go to the Auth Settings of the App and add the following URL to the "Authorized redirect URLs"
- - `{your_domain}/idps/callback`
- - Example redirect url for the domain `https://acme.zitadel.cloud` would look like this:  `https://acme.zitadel.cloud/idps/callback`
+ - `{your_domain}/ui/login/login/externalidp/callback`
+ - Example redirect url for the domain `https://acme.zitadel.cloud` would look like this:  `https://acme.zitadel.cloud/ui/login/login/externalidp/callback`
 5. Verify the app as your company
 6. In the Auth - OAuth 2.0 scopes section you should see `openid`, `profile` and `email` listed
 7. Save Client ID and Primary Client Secret from the Application credentials

docs/docs/guides/integrate/identity-providers/okta_saml.mdx

@@ -35,7 +35,7 @@ As an alternative you can add the SAML identity provider through the API, either
 
 After you created the SAML Provider in ZITADEL, you can copy the URLs you need to configure in your OKTA application.
 
-![OKTA SAML App URLs](/img/guides/zitadel_saml_provider_urls.png)
+![OKTA SAML App URLs](/img/guides/zitadel_okta_saml_provider_urls.png)
 
 ## OKTA Configuration