feat: on ACR change keep authentication context if custom script allows to do this

Currently on ACR change when client force to user re-authentication with script which has bigger priory server clean authentication context. We can keep it in some case to allow new ACR to reuse this data. For example, to skip user/pwd authentication step.

In order to to this we need to add new method to authentication script:

    boolean keepContextOnNewRequest<String, SimpleCustomProperty> configurationAttributes, Map<String, String[]> requestParameters, Map<String, String> sessionIdAttributess, String currentAcr, String newAcr);

Server should call this method only if script getApiVersion() > 14 in order to avoid issues with existing scripts which not have this method.

If keepContextOnRequest returns True server should mark session context as unauthenticated and call authenticator to resume flow. Inside this method script can call identity.getWorkingParameters() to reconfigure authentication context. For example clean data for all steps except user/pwd authentication steps. Also script can modify sessionIdAttributess to start authentication from specific step.
In other case server should do same flow which it has now.