OPENTHREAD_CONFIG_SRP_CLIENT_DISALLOW_SERVER_SWITCH_WITH_REGISTERED_HOST macro

@def OPENTHREAD_CONFIG_SRP_CLIENT_DISALLOW_SERVER_SWITCH_WITH_REGISTERED_HOST Define to 1 to disallow SRP client to switch server (when auto-start is used) on failure if host (or any services) were previously successfully registered with the currently selected server. This config is only applicable when `OPENTHREAD_CONFIG_SRP_CLIENT_SWITCH_SERVER_ON_FAILURE` is enabled. If this is enabled, once SRP client successfully registers with an auto-start selected SRP server, it stays with the selected SRP server (even if future SRP updates fail or timeout) while the related server entry remains present in the Thread Network Data. If the entry is removed from Network Data, then SRP client will try to select a new server. Enabling this behavior would be useful allowing more aggressive switch logic (e.g., switch after fewer timeouts `OPENTHREAD_CONFIG_SRP_CLIENT_MAX_TIMEOUT_FAILURES_TO_SWITCH_SERVER`) while not allowing switch due to temporary failures on the currently selected server. This can help avoid situation where the old server may still remember the registered host/service info and client switching to a new server then failing due to name conflict (when new server probes for the host/service name original server would not allow new registration).