Make compatibility mode for oidc logout endpoint fully compatible to previous keyloak versions

### Description

This is about backport of https://github.com/keycloak/keycloak/issues/13469 to Keycloak 19.0.2.

There is also documentation PR https://github.com/keycloak/keycloak-documentation/pull/1658, which should be backported as well.

### Discussion

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### Motivation

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### Details

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