fix: remove restart login flow for clients with multiple idps and allow sso

[NithinKuruba]

SSO Across Clients with Shared IDPs:
Users can now perform Single Sign-On (SSO) across both single and multi-IDP clients. If a user is authenticated with IDP A on Client A, they can seamlessly access Client B using the same IDP A, provided that IDP A is allowed for Client B. This also applies to a case where Client A is single IDP and Client B is a multi IDP with one common IDP.

Session Handling for Clients with Distinct IDPs:
When switching between clients that use entirely different sets of IDPs (i.e., no shared IDPs), only the most recent Keycloak session is retained. The previous session is invalidated, effectively logging the user out of the earlier client.

Direct IDP Login via KC_IDP_HINT:
Using the KC_IDP_HINT parameter still enables users to bypass the Keycloak login screen and land directly on the specified IDP’s login page.

[NithinKuruba]

Invalid PR, so creating a new one and closing this one.